History and Basic Design of .223 and 5.56 Ammunition.



Q. What is the history behind the development of the .223/5.56mm round? Studies of the fighting in WWII determined that most of the infantry fighting took place at distances under 200 yards, and those figures have not changed much in modern conflicts.(1) This was a revelation at the time and a controversial one, as ever since the development of smokeless powder, the long distance capabilities of military rifles had been stressed. It was common for rifles designed in the 1890s through the 1940s to have sights adjustable out to 1,000 or even 2,000 yards, and often not having an adjustment below 200 or 300 yards. Obviously, there was a discrepancy between the design of these rifles and how they were most often used. Following WWII, the US military decided it needed a select-fire, detachable-magazine rifle. (The WWII-era M1 Garand had originally been designed with a detachable magazine, but at the time, the military decided they were a liability for a standard, front-line infantry rifle and had the M1 redesigned.) During this period during the late 40s and early 50s, many nations were experimenting with smaller-caliber rifles that were controllable in full-auto and allowed more rounds to be carried. The US military insisted on a 30 caliber rifle, though, and merely shortened the existing .30-06 Springfield (7.62x63mm) round to create the 7.62×51mm round, which Winchester released commercially as the .308 Winchester. The US also forced this round onto the newly-formed NATO, over protests that it was too much cartridge, would require rifles to be too heavy, and wouldn't be controllable on full auto. The first point is arguable, but the last two were certainly true. Still, the US military, having determined that the Belgium-designed FN FAL was a better rifle then the domestic M14 (a modified M1 Garand), chose the M14 anyway. Such is politics. The M14 program was a political minefield and during the early 1960s, minor US involvement as "advisors" in the southeast Asian country called Vietnam was beginning to escalate. It didn't take long before the Vietnam expansion, coupled with manufacturing problems with some M14 contractors, resulted in too many soldiers and too few M14s. The military initially pulled WWII M1 Garands out of storage and pressed them back into service, but these long, heavy rifles were poorly suited to the jungle environment of Vietnam. During this time, Eugene Stoner of ArmaLite, the armament division of Fairchild Aircraft, had designed a rifle called the ArmaLite Model 10, or AR-10, which was chambered in the current NATO round of 7.62×51mm. Though the AR-10 was produced too late to enter the M14 competition, ArmaLite hoped to sell the AR-10 to foreign militaries. Meanwhile, there was a faction of the US Military and the Congress which supported the idea of a lightweight, select-fire rifle firing a mid-power, small-caliber, high-velocity (SCHV) cartridge. After seeing the ArmaLite AR-10, they discussed their desire for a scaled-down model. ArmaLite engineers Jim Sullivan and Bob Fremont scaled down the AR-10 to fit the hot varmint cartridge of the day, the .222 Remington. During some preliminary military testing, it was decided that the .222 Rem wasn't quite powerful enough. Though the .222 Remington Magnum existed and had the power they were looking for, the severe shoulder angle would have prevented positive feeding in a semi-auto, and so it was decided that the best solution was to lengthen the .222 Rem case. The result was the 5.56×45mm cartridge, designed by G. A. Gustafson, which Remington released commercially as the .223 Remington. This cartridge has virtually identical ballistics as the .222 Mag and, over time, the wide availability of .223 guns and ammo has lead to the demise of the .222 and .222 Mag cartridges. The AR15 was initially adopted by the Air Force, but the need for rifles for soldiers heading to Vietnam gave the "medium-power cartridge" supporters an opening and the AR15 rifle was hastily procured, initially as a one-time purchase. Continued problems with the M14 program lead to the official adoption of the AR15, which was given the US military designation "M16." Fact: The national average engagement range for police 'snipers' has, for the past 20 years, been 78 yards. The FBI Hostage Rescue Team (HRT) snipers are limited to engagement ranges of 200 yards. The longest recorded shot taken by a police marksman in the US is 97 yards. (There are some reports that indicate some longer shots, including one alleged 300 yard shot in 1982 by the U.S. Park Police in response to a bombing threat at the Washington Monument- but these are very rare and not confirmed). The FBI's uniform crime report indicates that the average engagement range in a handgun incident is between 7 and 10 feet. For a more detailed history of the M1 Garand see: The Complete Guide to the M1 Garand and the M1 Carbine, by Bruce N. Canfield. For a more detailed history of the M16, see: The Black Rifle: M16 Retrospective, by R. Blake Stevens. For more details about the history of the 5.56x45mm round itself, see A 5.56×45mm "Timeline" by Daniel E. Watters on Dean Spear's The Gun Zone.

Q. What is the difference between 5.56×45mm and .223 Remington ammo ? In the 1950's, the US military adopted the metric system of measurement and uses metric measurements to describe ammo. However, the US commercial ammo market typically used the English "caliber" measurements when describing ammo. "Caliber" is a shorthand way of saying "hundredths (or thousandths) of an inch." For example, a fifty caliber projectile is approximately fifty one-hundredths (.50) of an inch and a 357 caliber projectile is approximately three-hundred and fifty-seven thousandths (.357) of an inch. Dimensionally, 5.56 and .223 ammo are identical, though military 5.56 ammo is typically loaded to higher pressures and velocities than commercial ammo and may, in guns with extremely tight "match" .223 chambers, be unsafe to fire. The chambers for .223 and 5.56 weapons are not the same either. Though the AR15 design provides an extremely strong action, high pressure signs on the brass and primers, extraction failures and cycling problems may be seen when firing hot 5.56 ammo in .223-chambered rifles. Military M16s and AR15s from Colt, Bushmaster, FN, DPMS, and some others, have the M16-spec chamber and should have no trouble firing hot 5.56 ammunition. Military M16s have slightly more headspace and have a longer throat area, compared to the SAAMI .223 chamber spec, which was originally designed for bolt-action rifles. Commercial SAAMI-specification .223 chambers have a much shorter throat or leade and less freebore than the military chamber. Shooting 5.56 Mil-Spec ammo in a SAAMI-specification chamber can increase pressure dramatically, up to an additional 15,000 psi or more. The military chamber is often referred to as a "5.56 NATO" chamber, as that is what is usually stamped on military barrels. Some commercial AR manufacturers use the tighter ".223" (i.e., SAAMI-spec and often labeled ".223" or ".223 Remington") chamber, which provides for increased accuracy but, in self-loading rifles, less cycling reliability, especially with hot-loaded military ammo. A few AR manufacturers use an in-between chamber spec, such as the Wylde chamber. Many mis-mark their barrels too, which further complicates things. You can generally tell what sort of chamber you are dealing with by the markings, if any, on the barrel, but always check with the manufacturer to be sure. Typical Colt Mil-Spec-type markings: C MP 5.56 NATO 1/7 Typical Bushmaster markings: B MP 5.56 NATO 1/9 HBAR DPMS marks their barrels ".223", though they actually have 5.56 chambers. Olympic Arms marks their barrels with "556", with some additionally marked "SS" or "SUM." This marking is used on all barrels, even older barrels that used .223 chambers and current target models that also use .223 chambers. Non-target barrels made since 2001 should have 5.56 chambers. Armalite typically doesn't mark their barrels. A2 and A4 models had .223 chambers until mid-2001, and have used 5.56 chambers since. The (t) models use .223 match chambers. Rock River Arms uses the Wylde chamber specs on most rifles, and does not mark their barrels. Most other AR manufacturers' barrels are unmarked, and chamber dimensions are unknown.







Opinion: In general it is a bad idea to attempt to fire 5.56 rounds (e.g., M193, M855) in .223 chambers, particularly with older rifles. Fact: SAAMI specifically warns against the use of 5.56mm ammo in .223 chambers. The .223 SAAMI specification was originally made with bolt rifles in mind. For more see the SAAMI website ammo warning.

5.56 v. .223 Remington specification. Fact: The different manufacturer's chamber types are listed at length and in great detail at: The Maryland AR15 Shooters Site.

Q. Which should I be looking for in an AR15, a 5.56 NATO or .223 Remington chamber? This is really a matter of the role for which you plan to use your AR. .223 Remington chambers will give you slightly better accuracy, which is important for a match or varmint rifle. Any loss of feeding and cycling reliability and the restriction against shooting military ammo isn't as important as the accuracy gains for a rifle used in these roles, because for these rifles, accuracy is everything. People who just want to plink or who plan to shoot military ammo (such as most of the cheap surplus ammo available), and especially those who may use their AR as a weapon, should choose 5.56 chambers.



Opinion: Unless you have a reason to seek out .223 Remington SAAMI spec chambers, 5.56 NATO is probably the best solution. 5.56 NATO chambers still can have outstanding accuracy and give you more flexibility in ammo selection.

Q. What is the circle-cross stamp on some of my ammo? The circle-cross Å is the NATO symbol. It indicates that the ammo was loaded in a NATO-approved facility and meets the NATO specifications for that round. Note that NATO specifications are not the same as US military specifications and that many NATO-approved rounds do not meet US military specs. US military specs (such as M193 and M855) have additional requirements, such as minimum velocities, that the NATO specs (like SS-109) don't have. Fact: There are some exceptions to this rule. For example, recent Lake City and Winchester M193 is loaded in cases marked with the NATO circle-cross. This is done simply to save money by having one production run of cases instead of two. M193 was never adopted by NATO; by the time NATO decided to standardize on 5.56mm, the SS-109/M855 ammo was available, and was adopted as the standard. M193 is still "Mil-Spec," it just isn't "NATO" spec.

Q. How can I tell if a round is SAAMI, US military, or 5.56 NATO Mil-Spec? Generally if the round is an M193, M855, M196, M856, or SS-109 round it is Mil-Spec. This FAQ will help you determine the differences between these specs. Often Mil-Spec rounds sold commercially have similar model numbers, like XM-193. Another good clue (but not definitive evidence) is the presence of the NATO cross in a circle on the headstamp. Ammo that has a painted tip (Green for M855) is generally always military ammo. Generally you don't have to worry unless you're using a .223-chambered rifle, but it's a good idea to check regardless. Of course, if you have a Mil-Spec chamber, you needn't bother. NOTE: All bets are off if the ammo in question has been "remanufactured" or "reloaded." There's no way to know what you've got with reloads, other than the reputation of the reloader.



NATO stamp on a Lake City 5.56 round from www.ammoman.com.

Q. What is FMJ? JSP? JHP? FMJBT? FMJ is "Full Metal Jacket" and is used to describe rounds that are entirely encased (except for the bullet base, typically) in a metal jacket, usually copper alloy called gilding metal. FMJ rounds are also sometimes referred to as "ball" (meaning "standard") ammunition by the military. Generally these rounds are designed with little to no expansion in mind. They are comparatively inexpensive to produce, feed well, give good penetration in most materials. The jacketed nose prevents bullet expansion and typically leaves the bullet intact after striking flesh (the 5.56 round is a notable exception). JSP is "Jacketed Soft Point" and is used to describe rounds that are encased in a metal jacket, again, usually gilding metal, but leave the soft lead core exposed at the tip of the bullet. The soft nose deforms upon striking dense mediums, and these rounds are generally designed to expand rapidly at the nose and mushroom, ensuring that the center of gravity stays in front, and causing the bullet to continue traveling forward through the target. The larger frontal surface area causes more tissue disruption compared to most non-expanding bullets. JHP is "Jacketed Hollow Point" and is used to describe rounds that are encased in a metal jacket, gilding metal again, but have a small cavity in the nose along with a round opening in the jacket in the nose. JHP rounds are also designed for expansion but tend to have faster "mushrooming" effects because the hollow point is filled with high-pressure material when the bullet impacts, often peeling back the jacket and making a "mushroom" shaped projectile. BT stands for "Boat Tail" and refers to the base of the bullet. A "Boat Tail" is a sloping end which narrows gently at the base of the bullet, so that the cross-section resembles the shape of a boat's hull. The boat tail shape reduces drag on a bullet, helping it to retain velocity and resist deflection from crosswinds, but causes the bullet to take longer to "settle" after leaving the barrel compared to a standard "flat-base" bullet. Boat tail bullets are usually selected for long-range shooting, while the flat-base bullet shape tends to be more accurate at short ranges. A "HPBT" bullet is a "Hollow Point Boat Tail" bullet.





A FMJ bullet.

A JSP bullet.

A JHP bullet.

A HPBT bullet.

Q. What is "Ballistic Tip" ammo? "Ballistic Tip" is actually a trademark of Nosler, who first started making plastic tipped bullets in 1985. Though originally designed to prevent damage to the bullet nose when feeding (while the nose of a soft tip or hollow point might deform due during feeding to the soft lead content in the nose, a plastic tip bullet will maintain a consistent nose shape) today the primary advantage of a polymer tipped bullets is a high ballistic coefficient. The design also allows the center of gravity to be moved back, increasing in flight stability. This is the same design theory that gives hollow point match bullets better accuracy properties. In terminal performance, ballistic tips are designed to work like wedges, mashed into the hollow point and inside the jacket on impact, initiating expansion theoretically, quickly and reliably.









Polymer tips, left to right:

Hornady SST, Swift Scirocco and Nosler Ballistic Tip.

Q. What types of ammo has the US Military used in its M16s and M4s? The military has used the following ammo types in 5.56mm (excluding blanks and specialty rounds): M193 : 55gr FMJBT Ball, plain tip. This cartridge is intended for use against personnel and unarmored targets from 5.56×45mm weapons with a 1-in-12-inch (1:12) or faster rifling twist rate (M16 family rifles and other compatible systems). Its ballistic coefficient is typically .243

M196: 55gr Tracer, short range, red-painted tip. M855: 62gr FMJBT Ball, green-painted tip. This cartridge is intended for use against personnel, unarmored and light armored targets from 5.56×45mm weapons with a 1-in-10-inch (1:10) or faster rifling twist (Machine guns: M249 Minimi; Rifles: M16A2 and other compatible systems). The M855 cartridge is based on the FN-designed SS-109 bullet, and has a gilding metal-jacketed, lead alloy core bullet with a steel penetrator. The primer and case are waterproof. It was adopted by NATO in 1980 as the standard small arms ammunition for NATO forces. Its ballistic coefficient is typically 304. M856: 61gr Tracer, long range, orange-painted tip. This cartridge uses the FN-designed L-110, 63.7 grain tracer bullet, which has no steel penetrator. (Note that while FM 23-14 lists this bullet weight for the M856, IMI lists the weight of the L-110 tracer bullet which tops the M856 round as 61.7 grains. At least one AR15.com member reports 60.8-61.3 weights for a variety of M856 rounds that were pulled). The long projectile requires a barrel with a 1:8 or faster rifling twist. M995: 62gr FMJBT AP, black-painted tip. This FN-designed bullet uses a hardened tungsten-carbide penetrator, and is only available on special-issue SAW belts. M996: Actually, XM996, as it hasn't been adopted yet. The tracer compliment to M995.



Left to Right: M193, M855, M856, Sierra MatchKing HPBT.



Component view of M995 Armor Piercing 5.56mm. Fact: The specifications for the various rounds are: M193: Defined by: Mil-C-9963F

55 grain bullet (q 2 grains) at a muzzle velocity of 3,165 (q 40 fps) from a 20" barrel @ 78 feet from the muzzle. Accuracy: maximum of a two inch mean radius at 200 yards from ten 10 shot groups (~3 MOA). "Statistically average" M193 ranges from 1.2 to 1.6 inches mean radius, which is equivalent to 1.8 to 2.4 MOA. Velocity runs about 3,200 fps due to gas loss through the port. Accuracy is typically around 2 to 2+ MOA from an M16A1 rifle at ranges of 100 to 300 yards. M193 ammunition should have 1:12 twist or faster. M193 is barely stabilized with 1:14 at ambient temperatures and will not stabilize at all when the air temperature drops below freezing. M855: Defined in MIL-C-63989

NATO specifications for M855 Ball require a 61.7 grain (q 1.5 grains) with a hardened steel penetrator at a velocity of 3,000 fps (q 40 fps) from a 20" barrel @ 78 feet from the muzzle. Typical velocity 15 feet from the M16A2's muzzle is 3,100 fps. Accuracy: maximum of approximately four MOA over the 100 to 600 yard range. Typical accuracy of average lots in an M16A2 is about 2+ MOA. This round must also penetrate a nominal 10 gauge SAE 1010 or 1020 steel test plate at a range of at least 570 meters (623 yards). The M193 round will penetrate this same plate reliably at 400 yards and about half the time at 500 yards. The 5.56mm and 7.62mm NATO rounds will penetrate it reliably out to 700 yards or more. Because the steel penetrator increases the length and changes the weight distribution of the SS-109 bullet, it is suitable for use only in barrels with a twist of one turn in nine inches or faster. 1:10 twist will barely stabilize this round and not below zero degrees F. Reloaders: Both M855 and M193 in the US generally use Olin Ball WC844 propellant. Apparently H335 is roughly equivalent to WC844.

Cross sections of various rounds.

Q. What are the dimensional specifications for M855 and M193 casings?

M855 (Left) M193 (Right).

Q. What is SS-109? Is it the same as M855? SS-109 is Fabrique Nationale's (FN's) name for their 61.5 grain bullet with the steel penetrator in the nose and what they call rounds loaded with this bullet. (FN calls M193-type ammo "SS-92.") The US military's M855 round is loaded with the SS-109 bullet, though the US military has additional specifications that ammo must meet before it can be called M855. So, while all M855 is loaded with SS-109 bullets, all "SS-109 ammo" will not meet the M855 specs. For example, the British purposely underloaded some lots of their ammo in an effort to get their L85A1 (SA80) rifles to cycle properly. The ammo is still loaded with SS-109 bullets and labeled as SS-109, but it is nowhere near the M855 velocity specifications.





Diagram of M855 construction.

Q. What type of ammo is current issue for US Military forces? All front-line forces are armed with M16A2s and M4s and are issued M855 as standard-issue ammo. A few remaining Reserve and National Guard units, as well as some Air Force units, still carry M16A1s (you've probably seen them in the airports lately) and are issued M193 Ball (if they are issued any ammo at all) because of the difference in twist of the barrel. Some special forces units, particularly in Afghanistan and Iraq, are using Mk262 and Mk262 Mod1 ammo. These are rounds loaded with heavy (up to 77 grain) JHP match bullets, in response to some issues with M855 terminal performance. This continues a recent trend towards heavier rounds (69 grains and over) for improved terminal ballistic performance.

Q. What about Mk262 or Mk262 Mod1? Due to the poor performance of M855 ammunition, particularly in short-barreled carbines of 10.5-14.5" in length, Navy SEALs, and eventually other SOCOM units, began experimenting with using loads originally designed for marksmanship units for combat. It was soon discovered that while these loads were both very accurate and had excellent terminal ballistics even from short barrels, the loads weren't quite ideal for combat. The target bullets had no cannelure, and the bullets weren't crimped in place, which could allow bullet set-back during feeding and raise chamber pressures to dangerous levels. Further, most loads were of somewhat mild velocities, as the load was chosen with accuracy, not terminal ballistics, in mind. Sierra was asked to produce a bullet cannelured version, but they intially refused. Nosler did not have any problems putting a cannelure on their 77 gr bullet. Black Hills Ammunition was approached to make a slightly modified version of these loads for combat use. A cannelure was specified, the bullets were to be crimped, and the load was to be up to military chamber pressures, with maximum safe velocity being desired. The primers were to be crimped and sealed, and of course, overall length had allow for loading in standard magazines. The Marines (in conjunction with a large Federal LE agency) did extensive testing of this large experimental batch of BH loaded Nosler 77 gr cannelured OTM's in the Fall of 2002. It offered outstanding terminal performance out to the maximum test distance of 300 yards. They then ordered 1.1 million rounds of cannelured 77 gr OTM's via the existing Mk262 SOCOM contract (which did not specify a manufacturer) administered through Crane. The cannelured 77 gr load was designated Mk262 Mod 1, and the orginal Mk262 was re-designated Mk262 Mod 0.

According to one observer: "At this point bureaucracy, nepostism, and capitalism converged. Sierra realized they were about to lose a VERY LARGE contract and suddenly they agreed to make the 77 gr SMK with a cannelure. Crane pushed for Sierra to get the contract over Nosler, although the Nosler offered better terminal performance. On the other hand, in all fairness, the Sierra bullet was slightly more accurate out of government test barrels than the Nosler--both shoot nearly the same out of real rifles, such as the by then type classified Mk12 SPR." Therefore, while a few hundred-thousand rounds of 77 gr Nosler OTM was manufactured and used primarily for testing, the cannelured 77 gr SMK was used in the the multi-million round contract for the Mk262 Mod 1. Recently, Sierra agreed to add a minimal crimp to their bullet, and this has since replaced the Nosler bullet in the current versions of Mk262 Mod1. As of April 2004, Mk 262 Mod1 has seen extensive use in Afghanistan and Iraq, in carbines with barrels as short as 10.5", and has proven to be very effective at ranges that M855 is woefully inadequate from the same weapons. It is also commonly used in the Army's "Special Purpose Rifles" (SPRs), which are accurized 18"-barreled rifles used by soldiers with additional combat marksmanship training in a squad sharp-shooter role.

Q. Why did the US Military adopt M855 for the M16? M855 and M856 are newer rounds developed in the late 1970s by Fabrique Nationale (FN) of Belgium. FN was developing a new 5.56mm belt-fed machine gun they called the "Minimi" (Mini-Machinegun) for entry into the US military's Squad Automatic Weapon (SAW) program. The SAW was to augment, and in many cases replace, the 7.62×51mm M60 made by Saco Defense (now part of the General Dynamics Armament Division). Because there was a lot of resistance to giving up larger, longer-range round of the M60, FN focused on making the SAW perform better at longer ranges than existing 5.56 platforms (i.e., the M16). They did this primarily by developing new bullets: the SS-109 "ball" round and the L-110 tracer. The SS-109 bullet uses a "compound" core, with a lead base topped by a steel penetrator, all covered in a gilding-metal (copper alloy) jacket. The L-110 tracer bullet has a copper-plated steel jacket and like all tracer bullets, is hollowed out at the base and filled with tracing compound. Both bullets are much longer in length than the earlier 55gr bullets, especially the L-110 tracer, which was designed to trace out to 800m, verses 450m for the older M196 tracer round. Due to their increased length, these bullets require a faster rifling twist to be properly stabilized. The military settled on a twist rate of 1:7, which is a compromise between the 1:9 twist ideal for SS-109 bullets and the 1:6 twist ideal for L-110 tracers. Remember, the goal of these new bullets was improving long range performance. For example, the SS-109 bullet was proven to have better penetration of the then-current-issue steel helmet at 600m than the M80 "ball" ammo fired by the M60. The M80 ammo was not able to penetrate both sides of the helmet at that distance; the SS-109 bullet could. The L-110 tracers provided a visible trace out to 800m, which was seen as the maximum effective range of the SAW. These improvements in long-range performance satisfied the military and the US ultimately adopted the Minimi as the M249 SAW. They also adopted the new FN bullets and the US specs for the loaded rounds are called M855 and M856. About the time the SAW was adopted, the M16 "A2 revision" program was underway and it was decided to adopt the new SAW ammo (and its rifling twist) for the M16A2. As older M16A1 1:12 twist barrels were not able to stabilize the longer bullets, the new bullets had to be marked (in countries with older 1:12 rifles) in order to make sure that the new ammo wasn't used in the older rifles. M855 received green painted tips and M856 received orange. M193 is plain and M196 is red. Take a look at: Fabrique Nationale (FN) The Minimi from FN--precursor to the SAW.



The M249 Squad Automatic Weapon (SAW).

Q. So why don't all US military units carry M855? The original ammo for the M16 was M193, with a 55gr copper-jacketed lead-core bullet. The rifling twist on the first M16s was 1 turn in 14 inches, or 1:14. This twist rate was selected simply because it was the twist rate commonly used in the .222 Remington-chambered varmint rifles that the .223 round was based on. During tests of the M16 in arctic regions, it was found that the slow 1:14 twist wasn't fast enough to stabilize the 55gr bullet in the denser air. To correct this problem, the twist was tightened to 1:12 and all future M16s and M16A1s came with 1:12 barrels. The M855 round and particularly the M856 tracer round, are very long bullets and require a faster twist rate in order to be stabilized in air. Firing M855 from a 1:12-twist rifle would result in an understabilized bullet that would only fly straight for about 90 yards, then veer off as much as 30° in a random direction. In order to prevent soldiers from accidentally firing M855 in 1:12-twist rifles, M855/SS-109 was given a green-painted bullet tip. This allows M855/SS-109 to be differentiated from plain-tipped M193. M16A2s, A3s, A4s, M4s and M4A1s all have a 1:7 twist and can stabilize both M855 and M193.





Fact: Stabilization is a factor of caliber (bullet diameter), velocity, and bullet length, not bullet weight.

Q. Is all SS-109/M855 ammo marked with green bullet tips? No. Countries that previously issued 5.56mm rifles with a 1:12 barrel twist will mark their SS-109/M855 ammo with (usually) green bullet tips, to prevent the ammo from being accidentally fired in the older 1:12 rifles. Also, countries that regularly supply other countries with older 1:12 rifles usually mark their bullets for the same reason. Countries that didn't adopt 5.56mm rifles until the NATO SS-109 standard was adopted usually don't mark their ammo with green tips, as they don't have any old 1:12 rifles to be concerned with. Note that many other countries that now use 5.56 weapons were still using 7.62mm rifles until recently and never used any other ammunition than the SS-109/M855 and L-110/M856, so they don't mark their bullets with green or orange paint unless they intend to sell it to countries who require these markings (the US, Germany, and Belgium, primarily). They also typically refer to their rounds by the FN bullet name.

Performance of .223 and 5.56 Ammunition.



Q. I have my rifle zeroed with M855 ammo. Will any 62gr ammo shoot the same? No. While M855 uses a 62gr bullet, it is a longer bullet due to the steel penetrator in the front of the bullet core. Steel is less dense than lead, so more volume of steel is needed to end up with the same weight (mass). There is also a small air cavity in front of the penetrator, unlike a bullet with a solid lead core. Any non-M855/SS-109 62 grain ammo (such as Wolf and Federal's American Eagle 62gr FMJ offerings) will have a solid lead core, and the resulting bullet will be significantly shorter than an SS-109 bullet. That means you can expect trajectory and penetration performance to differ as well.

Q. Do M193 and M855 shoot to the same point of impact? No... ...but within 300 yards, they're generally close enough (for combat use) that rezeroing isn't necessary. Obviously, you wouldn't want to switch from one to the other for a match without rezeroing. Consider the graphs below with battle zeros for each round. (250m zero for M193, 300m zero for M855).

Even out to 300 meters there is a mere 4.5 inch difference between the paths of the rounds.





The big differences in bullet path are past 400 meters.

A: M16A1 firing both M193 and M855, zeroed for M193.

B: M16A2 firing both M855 and M193, zeroed for M855.



Fact: The Scoop from the Army's Ammunition Information Notice (61-01) "INTERCHANGEABILITY OF 5.56MM BALL, TRACER AND BLANK AMMUNITION." Do not zero M16A2, M16A3 rifles or M4 and M4A1 carbines with M193 and then fire M855/M856 as performance will be affected. Fact: Generally M193 is zeroed out to 250 meters for the flattest trajectory. Using that "battle zero" the round is never more than 4 inches from the point of aim until almost 300 meters. By contrast M855 is usually "battle zeroed" to 300 meters. With this zero the M855 round is never more than 6 inches from the point of aim until 325 meters. Comparing the bullet paths with these zeros out to 300 meters, we find that M855 is about 5 inches higher than M193 at 300 meters.



M855 (left) and M193 (right).

Q. OK, what is all this stuff about rifle twists and different ammo? Rounds in flight spin for stability because of the rifling on the inside of the barrel. Depending on how much they spin, they are more or less stable in their flight and therefore more or less accurate. The earliest AR15s from the early 1960s had a twist rate of 1 complete twist every 14", or 1:14. This was increased to a twist rate of 1 turn in 12" for the M16, XM16E1, M16A1, and later rifles and carbines. The current M16A2s and up and the M4 carbines have a much faster twist rate, 1 turn in 7". The reason for the 1:7 twist is mainly to stabilize the M856 tracer bullet, which is much longer than other bullets. You will recall from above that the M856 was designed to provide 800 meters of trace out of the SAW. While the slow 1 in 12" twist is adequate to stabilize the 55 grain M193, it will not stabilize the 62 grain M855. As a result, the newer M855 ammo will group 1-2 feet at 100 yards, with bullets flying through the air sideways, instead of shooting to about 2" at 100 yards, like military ammo should. All this has some ramifications for ammunition selection depending on your rifle's rate of twist. You can also overspin projectiles and cause overstability. This results in the not-so-desirable condition that keeps the nose of the round pointed high, as illustrated below:

You can also spin them so hard they fly apart. That's rare, but it happens if you are dealing with very tight twists and very high velocities. When fired at 3200 fps in a 1-in-7 twist rifle, a round is rotating at over 300,000 rpm when it leaves the muzzle. Light, thin-jacketed varmint bullets (i.e., 40gr Hornady TNT or Federal Blitz bullets) often can't take that much spin and will pull themselves apart. Fact: Generally you want a gyroscopic stability factor (Sg) of 1.3 or greater in a given round, about the low end for normal shooting. You get this on the larger M855 round with a 1 in 9" twist. By comparison a 1 in 10" twist will keep that M855 round down to about 1.2- not enough if it starts to get cold. Really you want stability to be between 1.5 and 2.0- a 1 in 8" twist on a M855 round. In actuality a 9" twist is a bit better for accuracy as it doesn't spin up non-balanced bullets too fast causing them to wobble in flight. If you have match rounds, well balanced and tested, you don't really have to worry about overtwisting until you hit 5.0 or so.

The result of unstabilized bullets:

A 1 in 12" FN-FNC firing M855 at 100 yards.

(Note the profiles cut out of the target). Math and Physics: A spin-stabilized projectile is said to be gyroscopically stable, if, in the presence of a yaw angle, it responds to an external wind force with the general motion of nutation and precession. In this case the longitudinal axis of the bullet moves into a direction perpendicular to the direction of the wind force.



It can be shown by a mathematical treatment that this condition is fulfilled, if the gyroscopic stability factor (SG) exceeds unity. This demand is called the gyroscopic stability condition. A bullet can be made gyroscopically stable by sufficiently spinning it. As the spin rate decreases more slowly than the velocity, the gyroscopic stability factor, at least close to the muzzle, continuously increases. Thus, if a bullet is gyroscopically stable at the muzzle, it will be gyroscopically stable for the rest of its flight.

Q. OK, that's complex. Simple question: Can I fire M193 ammo in my 1:7 or 1:9 twist barrel? Yes. M193 is essentially a "universal" round; able to be stabilized by barrels with twists between 1:14 and 1:7. Point of impact will change slightly compared to an M855 zero, so rezeroing is recommended. Fact: The Scoop from the Army's Ammunition Information Notice (61-01) "INTERCHANGEABILITY OF 5.56MM BALL, TRACER AND BLANK AMMUNITION." It is acceptable to use M193 and M196 ammunition in training in M16A2, M16A3 rifles and M4 and M4A1 carbines (16 percent range reduction). Substituting between types of ammunition during firing is not recommended.

Q. Can I fire M855/SS-109 in my 1:12 twist barrel? Yes, but... ...it won't be stabilized properly and after 90-95 yards, it will typically veer off in a random direction. You often won't hit paper at 100 yards. Though it won't hurt your rifle to fire this ammo, it is not recommended. Military manuals warn that it should only be fired in 1:12 twist barrels in a "combat emergency." Fact: The Scoop from the Army's Ammunition Information Notice (61-01) "INTERCHANGEABILITY OF 5.56MM BALL, TRACER AND BLANK AMMUNITION." "Cartridges M855 and M856 ammunition are extremely inaccurate when fired in the M16 and M16A1. The M16 and M16A1, with their 1:12 twist, do not impart enough spin on the heavier M855/M856 projectile to stabilize it in flight causing erratic performance and resulting inaccuracy. Therefore, while safe to fire in M16 and M16A1 they should only be used in an combat emergency and then only for close ranges 91.4 meters (100 yards) or less."

Q. Will M193 be accurate in a 1:7 or 1:9 twist barrel? It may be marginally less accurate due to the fast twist rate, particularly in 1:7 twist barrels. Unless you're trying to use these rounds for benchrest shooting, though, it shouldn't be enough to matter. A bullet's flight is disrupted slightly as it leaves the barrel and after traveling some distance, will "settle down" into an even spiral, similar to a thrown football. The faster a bullet is spinning, the longer it takes to settle down. The most accurate twist rate for any length of bullet will be just a bit faster than what is required to stabilize it for its entire flight path (1.3 SG). But note that bullet quality plays a much bigger part in this equation. A uniform bullet will spin true; a non-uniform bullet will wobble and be inaccurate. As a general matter when shooting M193 or M855 (as opposed to match ammo) its better to err on the side of a faster twist rate. Regardless, both 1:9 and 1:7 twists seem to shoot M193 and M855 very well.





Fact: M855/SS-109 often has worse "wobble problems" because of the complex construction of the bullet. It's hard to seat the steel penetrator in the M855/SS-109 round exactly in center of the projectile. Most plants have good quality control for these rounds and spin them up in a balance test before sending them out the door but M193 and other simple cored rounds are usually more uniformly balanced.

Q. What twist rate do I want for my rifle? Probably 1:9, but it depends on what kind of bullets you intend to shoot. Special purpose rifles often have uncommon twist rates. For example, if you are building a varmint rifle and want to shoot the short 35 grain, 40 grain, and 50 grain bullets, a 1:12, or even 1:14 twist would be best. On the other hand, long range High Power shooters often select 1:8, 1:7.7, 1:7, or 1:6.5-twist barrels to stabilize the long 77, 80 and even 90 grain bullets used for 1,000 yard competition. Additionally, new testing of heavier rounds (68-77 grains) seems to show that they perform very well in simulated tissue and may be a better defensive choice than 55 grain or 62 grain rounds. The majority of shooters, though, typically shoot bullets of 50 to 69 grains in weight (note that the 62gr SS-109/M855 bullet is as long as a 71 grain lead core bullet) and should select 1:9 twist barrels. At typical .223 velocities, a 1:9 twist will stabilize bullet lengths equivalent to lead-core bullets of 40 to 73 grains in weight. 1:12 twist rifles cannot stabilize SS-109/M855 bullets and 1:7 twist rifles are slightly less accurate with lighter bullets and will often blow apart the thin jackets of lightweight varmint bullets. The 1:7 twist is used by the military to stabilize the super-long L-110/M856 tracer bullet out to 800 yards, but unless your plans include shooting a significant amount of M856, the 1:9 twist rate is better suited for general use. There is, of course, an exception: if you want to use loads utilizing the heavier, 75-77 grain match bullets currently used by Spec-Ops troops and other selected shooters, you'll want a 1:7 twist barrel. Although military loadings using these bullets are expensive and hard to get, some persistent folks have managed to obtain a supply, and will need the proper barrel twist to use them. Anyone who foresees a need to shoot this ammo should consider a 1:7 twist barrel. Opinions (Pro and Con): 1:9 is best.

Why? Flexibility. It doesn't seem to have any problems throwing M856 tracers around, unless it gets really cold, it wears better than 1:7 and it stabilizes more rounds than 1:12. Additionally, 1:9 rifles, even Mil-Spec chrome chambered and barreled, can attain 1.0-2.0 MOA out to 300+ meters. No, 1:7 and 1:8 are the best.

Why? Accuracy. For heavier and longer rounds during competition shooting, 1:8 and 1:7 twists are the best for heavy 77-80 grain rounds that I use to shoot competitively at 500-1000 meters. Who needs to shoot tracers anyhow? More importantly, heavier rounds are showing very good results in terminal testing and are proving to be much better defensive rounds.

Q. What about XM193 from Federal and Q3131A? I have heard that some of these don't meet military specifications, particularly with respect to sealant on the necks and primers? Most manufacturers who market "Mil-Spec" M193 like ammo are either taking "factory seconds" that would otherwise go to the military and packaging them for civilian sale or reducing the second inspection of rounds before distribution. Ammo destined for the government is tested in lot batches and the entire lot is rejected if the batches fail spec tests. Generally, this ammo is still excellent for both plinking and defensive use. XM193 and Q3131a in particular are exceptional rounds for all around civilian use and still show very reliable function in AR15s. Some AR15ers have noticed, however, that sealant or other small details are sometimes lacking for some lots of these rounds. Sealant in particular is not a critical component to average civilian sales and therefore if sealant problems develop in M193 rounds destined for military contracts (and therefore out-of-spec rounds) they are usually sold as civilian versions of M193 (e.g. XM193). It should be pointed out that this is no reason whatsoever to avoid these rounds. If you are really concerned about sealant or intend to use the rounds for long-term storage or quasi-military use where they are likely to see harsh and moist conditions do some testing on random samples of your lot for sealant. See also the testing done below in the Ammo Oracle.



NATO stamp on a Lake City 5.56 round from www.ammoman.com.

Q. Holy earache Batman! This Q3131A/Lake City XM193 is really loud and it launches a FIREBALL from my muzzle! Everyone at the range is looking at me now. What gives? Yep. Q3131A and XM193 are Mil-Spec M193. They mean business. They are loaded hotter than most commercial loads and you're likely to notice that as soon as you fire them--especially out of a 16" post-ban barrel without a flash hider, you are going to get quite a bit of blast and a fireball. Some M193 may have flash retardant, but it's just no match for a short barrel without a hider. Prepare yourself for surgery on your ears if you have one of those short barrels and a muzzle brake. Always wear eye and ear protection when shooting!

A wee bit of muzzle blast.

Q. But military ammo has flash retardant, right? Well, not exactly. This had a lot of us fooled too. Back in the early Vietnam period M193 called for flash retardant components to be included in the round. Despite this no current specification any of us are aware of calls for flash retardant in M855 or other military small arms rounds. After some references from former procurement officers and contractors it's pretty clear that current standards don't call for it. It's a toss up if there is any flash retardant in your rounds. Surplus M193 might contain retardant, but fresh M193 probably does not. The best way to find out is to test it.

Opinion: According to one ballistic researcher of note: "It seems that Picatinny Arsenal feels that flash suppressant might eventually cause a build up-in the gas tubes of M16 type weapons and cause the weapons to malfunction." He goes on to note sardonically: "...of course this will not happen since all the soldiers will be dead before this theoretical fouling problem occurs..."

Q. What sort of velocity and ballistics should I expect from military ammo? M193 should give you around 3200-3250 fps from the muzzle of a 20" weapon and around 3150 from a 16" weapon. M855 should give you around 3050-3100 from a 20" weapon and around 2950-3000 from a 16" weapon. Here's some Q3131A (M193) ballistic data, of course your mileage may vary: Altitude 1480 feet 70 degrees 50% humidity. 55gr FMJBT Average cD over velocities: .267 Range Velocity Energy Momentum Drop Bullet Path Time of Flight (Yards) (Ft/Sec) (Ft/Lbs) (Lb-Sec) (inches) (inches) (Seconds) 0 3250.0 1289.70 0.79 0 -1.50 0.000000 25 3161.2 1220.20 0.77 -0.1 -0.79 0.023399 50 3074.2 1154.00 0.75 -0.43 -0.29 0.047458 75 2988.9 1090.80 0.73 -0.98 -0.02 0.072201 100 2905.4 1030.70 0.71 -1.77 0.00 0.097652 125 2823.4 973.30 0.69 -2.83 -0.23 0.123839 150 2742.9 918.70 0.67 -4.15 -0.74 0.150790 175 2663.9 866.50 0.65 -5.76 -1.54 0.178536 200 2586.3 816.80 0.63 -7.68 -2.64 0.207109 225 2510.1 769.30 0.61 -9.93 -4.06 0.236545 250 2435.0 724.00 0.59 -12.52 -5.83 0.266882 275 2361.3 680.80 0.58 -15.47 -7.97 0.298160 300 2288.8 639.70 0.56 -18.82 -10.50 0.330422 325 2217.6 600.50 0.54 -22.58 -13.44 0.363712 350 2147.5 563.10 0.52 -26.78 -16.82 0.398081 375 2078.8 527.60 0.51 -31.45 -20.68 0.433578 400 2011.3 494.00 0.49 -36.63 -25.03 0.470258 425 1945.2 462.00 0.48 -42.34 -29.93 0.508177 450 1880.4 431.70 0.46 -48.63 -35.40 0.547394 475 1817.0 403.10 0.44 -55.53 -41.48 0.587972 500 1755.1 376.10 0.43 -63.09 -48.22 0.629972

And for a 16" barrel: Range Velocity Energy Momentum Drop Bullet Path Time of Flight (Yards) (Ft/Sec) (Ft/Lbs) (LB-Sec) (inches) (inches) (Seconds) 0 3100.0 1173.4 0.76 0.00 -1.50 0.00000 25 3014.2 1109.4 0.74 -0.12 -0.75 0.02454 50 2930.2 1048.4 0.72 -0.47 -0.24 0.04977 75 2847.7 990.2 0.70 -1.08 0.01 0.07574 100 2766.8 934.7 0.68 -1.95 0.00 0.10246 125 2687.4 881.8 0.66 -3.11 -0.30 0.12996 150 2609.4 831.4 0.64 -4.57 -0.89 0.15828 175 2532.7 783.3 0.62 -6.35 -1.81 0.18746 200 2457.3 737.3 0.60 -8.47 -3.06 0.21752 225 2383.2 693.5 0.58 -10.94 -4.68 0.24851 250 2310.3 651.8 0.56 -13.80 -6.67 0.28048 275 2238.7 612.0 0.55 -17.07 -9.08 0.31345 300 2168.3 574.1 0.53 -20.77 -11.91 0.34749 325 2099.2 538.1 0.51 -24.93 -15.21 0.38265 350 2031.3 503.8 0.50 -29.58 -19.00 0.41897 375 1964.8 471.4 0.48 -34.77 -23.32 0.45651 400 1899.6 440.6 0.46 -40.51 -28.20 0.49533 425 1835.8 411.5 0.45 -46.86 -33.69 0.53550 450 1773.5 384.0 0.43 -53.85 -39.82 0.57707 475 1712.7 358.2 0.42 -61.53 -46.63 0.62010 500 1653.6 333.9 0.40 -69.95 -54.19 0.66467 Buyer Beware: Velocities are measured from many different "standard" distances. "Muzzle velocities" are almost never actual velocities at the muzzle, but rather velocities at 10, 15 or even 78 feet. Often this can lead to confusion and to the frequent accusation that commercial ammunition's velocity claims on the box are overstated. It's also always a good idea to look at the conditions any velocity test was performed under. A 30 degree F difference in temperature can result in a 50fps difference at 100 meters. 1000 feet of elevation can result in 30-40fps of velocity difference.

Q. Will Military Ammo wear my favorite National Match/Elite Sniper/$5500 accurized AR rifle out faster ? Not Really. All shooting will cause wear. Each round you fire wears the barrel a little more and therefore will have some impact (however slight) on accuracy. This said, most barrels have a lifetime of around 10,000-15,000 rounds without much impact on groups. Your mileage, obviously, will vary. You can expect it to be a bit higher with chromed weapons, lower without. Match rifles often have tighter twists (and therefore more friction or wear) than non-match rifles. Match rifles generally don't have chromed barrels or chambers. Your chamber, if its a match chamber, is likely to be the larger issue. Tolerances in match chambers are tighter and more sensitive to wear. Old M16's use to show throat wear after as few as 2,500 rounds. All of this contributes to make wear a larger issue in match rifles than in non-match rifles. Obviously, higher velocity rounds will cause more heat and more wear on your weapon. 40 and 45 grain "varmint" rounds are particularly brutal to barrels because of their extremely high velocities (up to 3600 and 3700 fps in some cases). By the same token, Mil-Spec rounds probably cause slightly more wear than lower velocity, lower pressure commercial rounds. Certainly, if you are worried about wear you will want to avoid steel/nickel jacketed ammo, particularly in non-chromed barrels. Such bullets were intended to be used in chrome-lined military rifles and may cause accelerated wear in non-lined barrels. Remember that in addition to wear from use, cleaning, and particularly over-cleaning, causes quite a bit of wear. The wear in some obsessively cleaned rifles will exceed any wear from firing. Also, sometimes what appears to be barrel wear-related inaccuracy in chrome lined barrels can be cleared up by cleaning out the copper build-up "fouling" in the bore with a good copper solvent. Opinion: It all comes down to personal experience and preference. The highest tiers of competition replace their barrels multiple times in a shooting season. "Serious" competitors might expect a barrel replacement each year. How serious are you? How often can you afford to change out barrels? If you're THAT serious you'd stick with the same match ammo in that weapon that you use to compete and keep the round count very low. If not, then perhaps a few thousand rounds of surplus ammo in a year won't matter much. Opinion: Bushmaster indicates: Mil spec. SS109 ammo will not measurably increase barrel wear under semi-auto fire and our mil. spec. (chrome lined) barrel will outlast any sporting rifle barrel - period. More barrels are ruined from over cleaning - or careless cleaning - than are ever "shot out". Chrome lined barrels really only need to be detail cleaned when the groups start to suffer. Otherwise, a little powder solvent (or "Break Free" with CLP), and a few passes with a brush, clean the chamber well, dry everything off and apply a very light coat of "Break Free" or "Rem-Oil" and put it away. We have had barrels here go 20,000 rounds and still be within mil. spec. when treated this way. One FAQ author has a chrome lined Bushmaster that has seen 30,000+ rounds without a change on the upper that still shoots ~1.5 MOA at 100 meters.

Q. What is Moly? What is it good for? The term Moly refers to Molybdenum Disulphide. This is an extremely fine powder which acts as an inert lubricant between the bullet and the bore. It is coated onto bullets to reduce the friction incurred on the bullet as it passes down the bore. The reduced friction is said to prolong barrel life, increase velocity and the ballistic coefficient, and increase accuracy. The moly coating does not build up in the barrel, as each successive shot removes any excess material from the previous round. If you are worried about barrel break-in on new rifles, do not use moly to begin with. The extra friction from an uncoated bullet is necessary for proper break-in.

Moly coated rounds.

Q. Moly sounds hella-cool. I'm going to use it with all my rounds from now on! Slow down there chief, Moly isn't sliced bread or anything. The biggest downside is that Moly is hygroscopic  meaning it is capable of absorbing water from the air. This water is then trapped between the moly coating and the barrel, which is definitely not a good thing. A quick fix to this problem is to run an oiled patch through the barrel after each shooting session. The oil will block moisture from being absorbed. Moly is also extremely messy, and it likes to stick to everything. It is also easily rubbed off of bullets, leaving a slippery film on whatever it touches. With practice and experience, however, this can be minimized. The biggest threat to barrel life is not addressed by the use of moly coated bullets: Throat erosion. Throat erosion is not caused by the friction of the bullet, rather the high pressure and high temperature gases that are present in every shot. It is not very often that a rifle barrel wears out its rifling before it suffers from extensive throat erosion.



Terminal Performance of .223 and 5.56 Ammunition.



Q. So which ammo is better, M193 or M855? And what is all this discussion about fragmentation? Are these dumdum bullets? Now you've done it. This is quite a point of debate and you can easily start a flame war just by asking. But, in our view, and though it depends on the specific circumstances, in almost every case, the strengths of M193 are a lot more important than those of M855. Let's be clear. Neither M193 or M855 are match quality rounds. They certainly can get you near 1 MOA (minute-of-angle) accuracy closer up and 1.5-2.0 MOA farther out (200-300 meters) if your rifle does the job and you're helping it along. But since you're asking about military spec ammo and not match ammo, we assume you don't need hyper accuracy. For anything out to 300 meters both of these rounds are pretty accurate anyhow. If you need to reach out farther, well, you should maybe consider heavier match quality rounds or move up to 7.62×51mm. M193 and M855 are military rounds designed to be inexpensive to produce and effective against personnel. Framing the debate between the two, we assume the main criterion is: how effective are they against live targets as a self-defense ammo? That being said it's important to understand how they work against personnel. That means we first need to talk about wound ballistics. Despite what the media, Bruce Willis, and Arnold Schwarzenegger may suggest, the only certain way to incapacitate an attacker is to cause significant damage to the Central Nervous System, or cause enough loss of blood to shut down the attacker's higher (and potentially lower) brain functions. There are certainly psychological factors that might stop an attacker ("I've been shot!"), but depending on these is probably not a good idea, and discounts the possibility that the attacker's state of mind is altered chemically or emotionally to a point where being shot won't seem like that interesting a distraction. That means you want to: Penetrate deep enough to get to major organs or blood vessels.

Disrupt the tissue of those structures.

Encourage profuse bleeding and/or CNS damage. After a great deal of study, and the conclusion that their then-current 9mm duty loads were a failure for their purposes, the FBI set up a comprehensive set of ballistics testing protocols. These represent a very good model to judge a rounds performance by. The FBI protocols use 12 inches as a penetration minimum in calibrated ballistic gelatin and looked for consistent 12"-18" penetration as an ideal. As a general matter, major vessels and organs can be reliably damaged with 6 inches of penetration. Ideally, then, you want a wound profile that penetrates at least 12" and does most of its damage between 4" and 12" of penetration. Of course, its always more effective to leave entry and exit holes to encourage bleeding. Shot placement is always important as well. No round will do you any good in the wall next to the attacker. Unlike most FMJ rounds, M193 and M855's primary wounding mechanism is fragmentation. This is a good thing because without fragmentation these rounds otherwise would act like a ice pick and cause very little damage because of their small size. At the proper velocity, both M855 and M193 strike flesh and immediately begin to yaw (tumble). Contrary to rumor and popular media belief, this is not unique to these rounds. All FMJ bullets with tapered noses will tumble in flesh with enough velocity, because their center of gravity is aft of their length center--causing them to want to travel "tail first" in denser mediums (like water and tissue). If the rounds are moving fast enough when they yaw to about 90 degrees of their original trajectory the stress on the bullet from traveling sideways through a dense medium (tissue) will overcome the structural integrity of the bullet and it will start to break up. If the velocity is high enough this breaking up is pretty dramatic and causes equally dramatic wounds. This is because the fragments travel rapidly through the temporarily crushed tissue and tear it. Most tissue is very elastic and will stretch quite far before returning to its normal shape (this is called the temporary crush cavity) but the addition of quickly moving fragments makes permanent the cavity that might otherwise have returned after the impact and therefore creates a much larger wound.

The block of gelatin struck by the SA 1986 M193 round.

(Notice the wound cavity near the left side, where the round entered the block

and the pair of dark fragments near the top in the center of the block).

(Source: Tatjana and Derek F.) The most significant difference between M193 and M855 is that inside 100 meters or so M193 will yaw more quickly and fragment more substantially than M855. M193 also tends to be more accurate under 100 meters or so. M855, by virtue of its greater length, tends to catch up with M193 speed of yaw and degree of fragmentation outside of 100-150 meters or so. Unless you live in an area that is very open, flat, and not populated, the chances are far greater that you'll need effective close-range performance a lot more than the increased long distance performance that M855 is designed for. Remember also that even in large infantry engagements, the average range of engagement is less than 200 yards; 50 yards in jungle conflicts like Vietnam. How do you plan to have to use these rounds in a self defense situation? How far will an engagement be? Likely, if you are in a "lone actor" situation you won't want to press an engagement if it is at ranges of over 150 yards. Ideally, that's an "escape and evasion" mission, not a good target opportunity. This probably means you're going to be dealing with engagements inside 150 or even 100 yards. That's probably where "escape and evasion" turns into "engage the enemy." Of course, your mileage may vary.







Respectful discussion, a long standing tradition at AR15.com. Fact: Read about the FBI shoot-out that spawned FBI ballistics testing in earnest. Opinions (Pro and Con):

Fragmentation is an outstanding wounding mechanism.

Fragmentation causes significantly larger wound profiles with M193 and M855 (as well as lighter rounds like 50gr and 55gr JSP or JHP) than controlled expansion rounds do. The size of these wounds make torso hits devastating and in non-torso hits can cause enough vascular damage to increase the rate of "bleed out." The penetration of M193 and M855 in tissue is not compromised by the fragmentation either, as large portions of the round, particularly the nose, retain enough mass to penetrate out to 14.5" after fragmentation. Because effective rounds need to do the most tissue damage possible, fragmentation is an ideal wounding mechanism and gives the small 5.56mm round more "bang for the buck" than even 7.62mm rounds that don't fragment. Fragmentation is a weak and unreliable wounding mechanism; controlled expansion is where its at.

While fragmentation is effective in certain circumstances, it is unreliable at longer ranges. A failure to fragment in a FMJ round like M193 or M855 means the round becomes a glorified .22LR. For engagements outside of 200 meters, fragmentation is of limited utility because of lower velocities. Controlled expansion, the same mechanism used in most hollowpoint handgun rounds, is far better understood, predictable and does not require high velocities for its effect. Controlled expansion is a proven design with thousands of rounds performing well in a variety of circumstances from hunting to law enforcement. Using rounds that utilize controlled expansion increased the effective range of the AR15 and makes it a better, more flexible defensive weapon.

An unfired Mil-Spec M193 1986 South African surplus bullet and the same bullet type after a ~3150fps encounter with ballistic gelatin. About 98% of mass and over 150 fragments recovered.

(Source: Tatjana and Derek F.)

Q. So, velocity is a critical component for the wound profile. How fast must the bullet be traveling when it hits its target in order to fragment reliably? Testing by combat surgeon Col. Martin L. Fackler, MD (USA Medical Corps, retired), determined that M193 and M855 bullets need to strike flesh at 2,700 feet per second in order to reliably fragment. Between 2,500 fps and 2,700 fps, the bullet may or may not fragment and below 2,500 fps, no significant fragmentation is likely to occur. If there isn't enough velocity to cause fragmentation, the result is a deep, 22 caliber hole, except an area where the yawing occurred, where the diameter of the hole grows briefly to the length of the bullet.

M193 rounds after close encounters with ballistic gelatin

at various velocities. (Fackler)



Opinions (Pro and Con):

Fackler is a genius.

Dr. Fackler's work in simulated tissue (ballistic gelatin) has made it easy to understand why bullet designs work and why they fail. His common sense approach to ballistics research is invaluable in helping us select defensive rounds based on their real performance. Ballistic gelatin was developed to simulate the average of human tissue based on thousands of actual wounds, animal tests and battlefield surgeon observations (including by Dr. Fackler) and as a result is an effective medium to test round performance in. Fackler is a fraud/misinterpreted.

Fackler works with ballistic gelatin. I've never seen a block of gelatin commit a violent crime so I'm not very interested in shooting one. What counts is the proven performance of rounds in actual shooting incidents. Gelatin is not human tissue. There are no bones, cavities or other organ like structures in gelatin. Regardless, Fackler's work is overcited and used to support questionable theories about terminal performance. Decide for yourself by reading some of Fackler's work: Wounding Patterns of Military Rifle Bullets. Stockton - The Facts.

Q. At what range will M193 fragment? How about M855? Assuming true M193 or M855 ammo, velocity is the key. Velocity is dependent on barrel length and environmental conditions. As barrel length increases, the bullet is propelled faster by the expanding gasses in the barrel, imparting more velocity on the bullet, resulting in a longer range before a fired bullet drops below 2700 fps. A shorter barrel imparts less velocity, and therefore the bullet has less range. Temperature, altitude and humidity are other factors. As temperature or altitude increases, air becomes less dense and bullets travel faster. Contrary to common conceptions, as humidity increases air also becomes less dense and helps bullets retain velocity. It is important, then, to keep in mind that any statistics given can only be approximate and can be affected by a wide range of factors. But as a baseline, these numbers are what you could expect for 75° F, 25% humidity, at sea level, from various barrel lengths: Distance to 2700 fps 20" Barrel 16" Barrel 14.5" Barrel 11.5" Barrel M193 190-200m 140-150m 95-100m 40-45m M855 140-150m 90-95m 45-50m 12-15m As you can see, barrel length and ammo selection make a major impact on fragmentation range.



Opinions (Pro and Con): 14.5" and 11.5" barrels are great, why waste all that weight and effort lugging around something larger?:

Shorter barrels are critical to close quarters battle (CQB) and urban work. Here ranges are shorter and getting that barrel around corners and inside houses is tough enough without it being too long. All that velocity isn't necessary and I'm worried about overpenetration anyhow so it's a good thing to keep it under control. If I really am worried about low velocities I'll just switch to controlled expansion rounds. I wouldn't be seen with anything shorter than a 16" and I'd try to hide my face if friends saw me without a 20":

I need a more flexible weapon that allows me to get out to 200 meters when I have to. Additionally, fragmentation is critical to my philosophy about wound ballistics and I want as much of it as I can get. This means at least 16" on my barrels and 20" is better. 16" is plenty short enough for interior and urban work and it gives me the advantage of not having to worry about using my rifle for long shots on deer or for longer defensive engagements. Plus, if I had a true 14.5" barrel I'd just have to register it with the ATF as a short barreled weapon anyhow. Why should I have 16" of overall length and only get the benefit of 14.5" of that?

Q. So do both M193 and M855 fragment the same? How do their wound profiles compare to the FBI requirements? The same? Not exactly. They certainly behave in a similar way when they encounter tissue at the right velocities, but they aren't exactly the same. Generally M193 yaws a bit quicker and fragments a bit more completely inside of 100 meters or so.

Here's an M193 FMJ round which has yawed

80 degrees after penetrating an orange (3.25 inches).

(Note the nose is facing away from the camera). Of course, M193 also has higher initial velocities generally as well as a smaller, weaker bullet so its fragmentation is often more dramatic than in M855 at close ranges. Still, both do a lot of tissue damage over 2700 fps.

Wound profile of M193.

Wound profile of M855.

Cross-section of 1986 South African M193 wound profile from inch 3 to inch 4.

Bullet has yawed and fragmentation has begun in earnest.

(Source: Tatjana and Derek F.)

Cross-sections from inch 4 to inch 6. Notice the opening up of the wound profile,

the significant deposit of fragments and substantial tissue damage.

Cross-sections from inch 6 to inch 8. Note the closing of the wound profile

and the larger size of fragments. As you can see, the wound cavity left by M193 is impressive. The wound profile starts opening up somewhere inside of 3". It is full blown fragmentation between 4" and 7". A torso shot has a very high probability of doing very serious damage to organs, certainly punching a large hole in lungs and/or heart tissue. M193 does seem to have a bit better penetration than M855 as well. Typically the nose of the bullet ends up penetrating to 13-14.5", traveling backwards through tissue. Superimposing the 5"-6" depth wound cross-section on the human torso, adjusting for size, reveals the probable effectiveness of the round.

Representation of a M193 3100 fps torso strike 2.5" right of center mass (left).

Representation of a 3100 fps M193 torso strike 3.5" left and 2" below center mass (right)

Size adjusted to scale. Critical areas (in green) and area of maximum fragmentation and

tissue disruption (in blue). Clearly both strikes would result in serious damage to heart/lung tissue. The margin of error given by the large width and height of the M193 wound cavity is significant and may turn 2-3 MOA strikes which would be "near misses" in non-fragmenting or smaller wound cavity rounds into "hits." It's this massive cavity that makes many of us think fragmentation is the best wounding mechanism to try and take advantage of. Remember that the only thing that will cause "instant" incapacitation is damage to the central nervous system. If you miss the CNS, you have to cause enough blood loss to debilitate the threat. That makes the goal to do as much vascular damage as possible. Both M855 and M193 clearly meet FBI standards for penetration both in clothed and non-clothed strikes. Despite this, there is growing concern over M855's performance based on recent field experience and testing. Partially because of the complex construction of M855/SS109 rounds their terminal performance often varies from lot to lot. As much as 6 and 7" of penetration have been observed before bullet yaw with some M855. While FBI standards do not specify fragmentation or yaw distance when evaluating rounds, given the importance of fragmentation in 5.56 bullets we are inclined to discourage use of M855 as a defensive round in light of the terminal performance and yaw consistency problems it continues to demonstrate.



Fact: The details of the FBI test protocol:

Test Event 1: Bare Gelatin The gelatin block is bare and shot at a range of ten feet measured from the muzzle to the front of the block. This test event correlates FBI results with those being obtained by other researchers, few of whom shoot into anything other than bare gelatin. It is common to obtain the greatest bullet expansion in this test. Rounds which do not meet the standards against bare gelatin tend to be unreliable in the more practical test events that follow.

Test Event 2: Heavy Clothing The gelatin block is covered with four layers of clothing: One layer of cotton T-Shirt material (48 threads per inch); one layer of cotton shirt material (80 threads per inch); a 10 ounce down comforter in cambric shell cover (232 threads per inch); and one layer of 13 ounce cotton denim (50 threads per inch). This simulates typical cold weather wear. The block is shot at ten feet, measured from the muzzle to the front of the block.

Test Event 3: Steel Two pieces of 20 gauge, hot rolled steel with a galvanized finish are set three inches apart. The steel is in six-inch squares. The gelatin block is covered with light clothing and placed 18 inches behind the rear most piece of steel. The shot is made at a distance of I0 feet measured from the muzzle to the front of the first piece of steel. Light clothing is one layer of cotton T-shirt material and one layer of cotton shirt material and is used in all subsequent test events. The steel is the heaviest gauge steel commonly found in automobile doors. This test simulates the weakest part of a car door. In all car doors, there is an area, or areas, where the heaviest obstacle is nothing more than two pieces of 20 gauge steel.

Test Event 4: Wallboard Two pieces of half-inch standard gypsum board are set 3.5 inches apart. The pieces are six inches square. The gelatin block is covered with light clothing and set 18 inches behind the rear most piece of gypsum. The shot is made ten feet, measured from the muzzle to the front surface of the first piece of gypsum. This test event simulates a typical interior building wall.

Test Event 5: Plywood One piece of three-quarter inch AA fir plywood is used. The piece is six inches square. The gelatin block is covered with light clothing and set 18 inches behind the rear surface of the plywood. The shot is made at ten feet, measured from the muzzle to the front surface of the plywood. This test event simulates the resistance of typical wooden doors or construction timbers.

Test Event 6: Automobile Glass One piece of A.S.I. one-quarter inch laminated automobile safety glass measuring 15 x 18 inches is set at an angle of 45 degrees to the horizontal. The line of bore of the weapon is offset 15 degrees to the side, resulting in a compound angle of impact for the bullet upon the glass. The gelatin block is covered with light clothing and set 18 inches behind the glass. The shot is made at ten feet, measured from the muzzle to the center of the glass pane. This test event with its two angles simulates a shot taken at the driver of a car from the left front quarter of the vehicle and not directly in front of it.

Test Event 7: Heavy Clothing at 20 yards This event repeats test event 2 but at the range of 20 yards, measured from the muzzle to the front of the gelatin. This test event assesses the effects of increased range and consequently decreased velocity.

Test Event 8: Automobile Glass at 20 yards This event repeats test event 6 but at a range of 20 yards, measured from the muzzle to the front of the glass and without the 15 degree offset. This shot is made from straight in front of the glass, simulating a shot at the driver of a car bearing down on the shooter. In addition to the above described series of test events, each cartridge is tested for velocity and accuracy. Twenty rounds are fired through a test barrel and twenty rounds are fired through the service weapon used in the penetration tests. Two ten-shot groups are fired from the test barrel and two ten-shot groups from the service weapon used, at 25 yards. They are measured from center to center of the two most widely spaced holes, averaged and reported. Fact: The average human only needs to lose about 20% of blood volume (only 1 liter) to induce shock and lose consciousness. 50% (2.5 liters) almost always causes death. Severe damage to a major vessel can cause as much as 1.5 liters a minute in hemorrhaging.

The central and peripheral nervous systems. Fact: The spinal cord is about the thickness of your pinky. It probably doesn't make a good primary target.



Fact: According to the FBI the average human torso is 9 inches front to back. Physiologically, a determined adversary can be stopped reliably and immediately only by a shot that disrupts the brain or upper spinal cord. Failing a hit to the central nervous system, massive bleeding from holes in the heart or major blood vessels of the torso causing circulatory collapse is the only other way to force incapacitation upon an adversary and this takes time. For example, there is sufficient oxygen within the brain to support full, voluntary action for 10-15 seconds after the heart has been destroyed. (Urey W. Patrick, FBI Firearms Training Institute).

Q. Isn't 7.62 NATO much better for long range penetration than 5.56 anyhow? Why would I want to use 5.56 when I could send 7.62 downrange instead? Well, yes and no. For some penetration mediums like mild steel, M855 is actually superior. Consider a recent research report: The SS-109 can penetrate the 3.45mm standard NATO steel plate to 640 meters, while the 7.62mm ball can only penetrate it to 620 meters. The U. S. steel helmet penetration results are even more impressive as the SS-109 can penetrate it up to 1,300 meters, while the 7.62mm ball cannot penetrate it beyond 800 meters. The current production 7.62×51mm NATO ball cartridge has remained unchanged since its adoption by NATO in 1953. As typified by the U. S. M80 ball and the Belgian M77 ball, this cartridge propels a 147-grain cupronickel-jacketed lead bullet at a muzzle velocity of 2,800 fps (848 mps). Total cartridge length and weight are 2.80 inches and 386 grains, respectively. Utilizing a standard 22-inch barrel with a rifling twist of one turn in twelve inches (M14 rifle), the maximum effective range of the 7.62×51mm ball cartridge is listed as 620 meters (682 yards). The U. S. M80 and the Belgian M77 ball projectiles can penetrate the standard NATO 3.45 mm (.14 inch) thick steel plate up to a range of 620 meters and can penetrate one side of the U. S. steel helmet up to a range of 800 meters (880 yards). In barrier and fortification penetration tests, the 147 grain ball projectile can consistently penetrate two test building blocks. The new SS-109 cartridge propels a heavier 62-grain semi-armor piercing projectile at an initial velocity of 3,050 fps (924 mps). The improved projectile contains a 10-grain .182 caliber hardened steel penetrator that ensures penetration at longer ranges. The new projectile can penetrate the standard NATO 3.45mm steel plate up to a range of 640 meters (704 yards) and one side of the U. S. steel helmet up to a range of 1,300 meters (1430 yards). In tests of barrier and fortification penetration however, the steel penetrator of the SS-109 could not pierce any of the test building blocks. The primary advantages of the intermediate power 5.56×45mm NATO cartridge are summarized as follows: (1) the penetration and power of the SS-109 version are superior to the 7.62mm NATO and more than adequate for the 300-meter average combat range documented in actual battle (ORO studies): (2) the lower recoil generated by the 5.56mm cartridge allows more control during full automatic fire and therefore provides greater firepower to the individual soldier; (3) the lesser weight of the 5.56mm ammunition allows the individual soldier to carry more ammunition and other equipment; (4) the smaller size of the 5.56mm ammunition allows the use of smaller, lighter and more compact rifles and squad automatic weapons and; (5) the lethality of the 5.56mm projectile is greater than the 7.62mm projectile at normal combat ranges, due to the tendency of the lighter projectile to tumble or shatter on impact. In summary, the 5.56mm NATO provides greater firepower and effectiveness than the larger and heavier 7.62mm NATO. 5.56-mm NATO ammunition weight only 47% as much as 7.62 mm NATO ammunition. However: These comparisons however, do not consider the fact that the SS-109 uses a semi-armor piercing, steel-cored projectile, while the 7.62mm ball uses a relatively soft antipersonnel, lead-cored projectile. A semi-armor piercing 7.62mm caliber projectile, using second generation technology as the SS-109, would easily outperform the smaller SS-109 projectile in penetration tests at all ranges. With respect to barrier and fortification penetration tests, the 7.62mm ball projectile can consistently penetrate two test building blocks, while the SS-109 semi-armor piercing projectile cannot penetrate a single block. Read the entire article , 7.62 mm Versus 5.56 mm - Does NATO Really Need Two Standard Rifle Calibers? by Major Vern T. Miyagi.

Fact: Data on hundreds of shootings collected by the Army Wound Data and Munitions Effectiveness Team and data from civilian shootings with 7.62×39mm ammunition, like from the AK-47, bear out the less than stellar lethality of the round.



Fact: The 7.62×51 AP round penetrates 15mm of armor plate at 300m. It also penetrates 120mm Plexiglas helicopter protection, is highly effective on brick and concrete walls, and causes no significant barrel wear.

Q. Didn't tightening the twist rate from 1:14 to 1:12 reduce the wounding potential of M193? No... ...though unfortunately this is widely believed. When the M16 was first used in Vietnam, it was assumed that the smaller 5.56mm round would make much smaller wounds than the 7.62mm M80 round fired from the M14. Everyone was surprised to learn that M16 wounds were often much more severe. In order to explain this discrepancy, it was theorized that the slow 1:14 barrel twist made the bullet less stable in flesh and caused it to tumble, resulting in the large wounds. In fact, the slow twist only made the bullet less stable in air. Any pointed, lead core bullet has the center of gravity aft of the center of the projectile and will, after a certain distance of penetration, rotate (yaw) 180° and continue base-first. This is where the appearance of "tumbling" came from. The actual cause of the larger-than-expected wounds was not a result of this yawing of the bullet, but of the velocity of the bullet coupled with the bullet's construction. M193 bullets have a groove or knurl around the middle, called a cannelure. This allows the mouth of the case to be crimped on to the bullet, preventing the bullet from being pushed back into the case during handling and feeding. The cannelure also weakens the integrity of the bullet jacket. When the bullet struck flesh at a high-enough velocity, the bullet's thin jacket, weakened by the cannelure, could not survive the pressure of moving sideways through the dense flesh. Instead, the bullet would only rotate about 90°, at which point the stresses were too much for the bullet jacket and the bullet would fragment. The results were a wound that was far out of proportion to the size of the bullet. Yet, the twist rate of the barrel and therefore the rotation speed of the bullet, is not a factor in the fragmenting equation. M855 ammo works exactly the same way, though due to its heavier bullet, it has less muzzle velocity. Less muzzle velocity translates to a shorter range in which the bullet retains enough velocity to fragment, compared to M193. Fact: Flesh is as much as 1000 times denser than air and will cause a bullet to lose stability almost instantly. For M193 and M855 ammo, this typically occurs after 3-5 inches of flesh penetration, though this can vary. In order to spin the bullet fast enough to be stable in flesh, the barrel twist would have to be on the order of 1 twist every 0.012 inches, which would look like the barrel had been threaded instead of rifled.

Q. If I increase spin or barrel twist, won't that decrease wounding by making a round more stable in tissue? No. The importance of rate of twist in wounding is a frequent subject of what we politely call "ballistic myth." Any projectile that has a "center of pressure" forward of the center of gravity will tend to tumble. You can illustrate this to yourself by trying to balance a pencil on your fingertip. Spin, given to the projectile by barrel twist, puts a projectile into a state described as "gyroscopically stable." The projectile might be momentarily disturbed but will return to nose-forward flight quickly. To describe how stable a given projectile is we use the gyroscopic stability factor (Sg). Generally you want a factor of 1.3 or greater for rifle rounds. 1.5-2.0 is a generally accepted value for 5.56 rounds. For M193 the following variables apply: axial moment of inertia (A) = 11.82 gm/mm2

transverse moment of inertia (B) = 77.45 gm/mm2

mass (m) = 3.53 grams

reference diameter (d) = 5.69 mm Using the gyroscopic stability formula: Sg = A2 p2 / (4 B Ma) and assuming sea level we use an air density of 1.2250 kg/m^3 and discover that this this projectile will need on the order of 236,000 rpm for good stability (Sg > 1.3). At 3200 fps M193 is typically spun up to more like 256,000 (1:9" twist) to 330,000 rpm (1:7") so that Sg approaches 1.9 or 2.0. 1:12" rifles will spin rounds at around 192,000 rpm and 1:14" rifles around 165,000 rpm. You can see why 1:14" rifles might have had trouble stabilizing M193 rounds. Clever math types will see that density of the medium traversed (air in this case) has a dramatic effect on the spin required to maintain the Sg (density being in the first term's divisor). This is why cold conditions tend to dip "barely stable" rounds below the stability threshold. Without doing too much calculus it will be seen that an increase of three orders of magnitude (1000) in this variable will be a dramatic one for spin requirements. To balance things spin must be increased to compensate. Through human flesh (which varies from 980 - 1100 kg/m^3 or about 1000 times the density of air) something on the order of 95,000,000 - 100,000,000 rpm is required to stabilize a projectile at speed. Given these differences it will be seen that the difference between a 1:12 or 1:14" twist when it hits flesh and a projectile launched from a 1:9 or 1:7" weapon is so small as to be beyond measuring. But the game isn't over yet. Gyroscopic stability of 2.0 or so is sufficient for a M193 projectile to recover from an upset quickly, return to nose-forward flight and not be over stabilized. To prevent the upset in the first place, particularly when a sudden and very extreme change in density (and therefore drag and pressure applied to the center of pressure) requires FAR more stability. To grant enough stability force to prevent the upset of a M193 projectile encountering a sudden 1000 fold increase in density a factor of as much as 10 to 50 times (speaking VERY conservatively) the required gyroscopic stability for a steady state flight through a medium of that density would be required. In other words, unless the projectile is spinning at nearly a BILLION rpm it is going to be upset by such a transition. Even at this rpm it is like to be upset somewhat. In summary, and to take the most extreme case, a M193 projectile spinning at 350,000 rpm (from a 1:7" rifle) is going to upset in flesh (yaw) exactly as fast as one spinning at 150,000 rpm (from a 1:14" rifle). Claiming that twist rate has any impact on the speed of yaw and therefore terminal performance is just not in line with the laws of physics. Anyone making such a claim should either be carefully avoided or introduced gently to basic gyroscopic stability concepts. Often a calming substance like warm milk or Thorazine helps in the transition of such a subject.

Q. Does the 2,700 fps rule apply to all .223 and 5.56 ammo? No. Velocity is only one factor, however important. Bullet construction is another. M193 and M855 fragment because the bullets have thin copper (actually "gilding metal," which is a copper alloy of roughly 90% copper and 10% zinc) jackets that are further weakened by a cannelure. It cannot be assumed that all bullets will fragment, or will fragment at the same velocity. Some examples: Czech-made Sellier & Bellot (S&B headstamp) ammo uses bullets with thicker jackets made of mild steel which have been copper-plated. From the outside, they appear just like M193 bullets, but due to the jacket material and construction, they do not fragment. Winchester 64gr Power Point ammo is loaded with a soft-point (SP) bullet with a thick copper jacket and no cannelure. It was specifically designed for hunting medium (deer) sized game and was designed to expand, but not fragment. M995 Armor Piercing ammo has a solid tungsten-carbide core. Tungsten is denser than lead, but much harder, and it won't fragment. Some time ago 7.62 NATO rounds manufactured in West Germany also had fragmenting properties. NATO standards do not specify jacket material or jacket thickness. The West German 7.62 round used copper-plated steel in the jacket, but their US counterparts used gilding metal alloy around .032 inches (.8mm) thick at the cannelure. The West German jacket is only about .020 inches (.5mm) thick near the cannelure. As a result of the differences, particularly the weaker jacket, the West German round yaws after 8cm or so in tissue before breaking in half at the cannelure. The nose, comprising just over half of the bullet's weight, generally remains intact, and the remaining mass of the lower half fragments. The result in tissue is predictably devastating. Many people wrongly assume that any ammo loaded with a 55gr FMJ bullet is the same as M193 ammo. This is false. Unless the ammo meets M193 specs, including both muzzle velocity and bullet construction, it can not be counted on to perform like M193. The same applies to 62gr ammo. Not all 62gr ammo is M855/SS-109.

Counter Opinion: Fackler's 2700fps rule for M193 is more like 2600fps.

Though the dramatic fragmentation seen over 2700 fps in M193 and M855 is clearly an effective wounding mechanism, the lesser fragmentation seen at 2600 - 2650 fps in M193 is still impressive. Wound channels from rounds at 2650 fps are certainly not as devastating as 2700+ fps but they are still larger than from controlled expansion rounds. Really, we should not be discounting the performance of M193 until its under 2600 fps. This should extend M193 fragmentation standards out to slightly over 200 meters from a 20" barrel and 150-175 meters from a 16" barrel.

A M193 round with cannelure indicated.



A West German 7.62 round (left) and the

American counterpart (right).

Q. That's really complicated. Simple question: Why is M193 better than M855? In a nutshell: Advantages of M193 over M855: It costs less, so you can buy more.

It's compatible with any rifling twist.

It's generally more widely available.

It has a slightly flatter trajectory with the appropriate battle zero.

It appears to have better terminal ballistics than M855. Though it isn't a bad idea to keep a couple of magazines worth of M855 in case you need to make a long-range (300+ yards) shot against a "hard" target (a vehicle or other equipment), most folks are better served with M193 for general use. Counter Opinion: Many optics (like some of the full size ACOGs) are calibrated to the ballistics of the 62gr M855 round, not the 55gr M193 rounds. Granted this is only a slight difference inside of 300 meters, but it will compromise the zero at longer ranges.

Counter Opinion: Keeping two kinds of ammo is rather foolish. It just leaves the opportunity open for confusion during a crisis, when it's most important to keep things simple.

Q. But doesn't M855 penetrate hard objects better than M193? It depends. At close ranges (up to 40-50 yards), M193 will penetrate thicker steel than M855, due to its increased velocity. Beyond 100 yards, M855's bullet construction starts paying off and it will penetrate better than M193. M855 also loses velocity more slowly than M193, with a cross-over point between 200 and 300 yards, beyond which M855 will have more velocity than M193.

Fact: Some penetration stats for M193 and 7.62 (M80):

Thickness of material for positive protection against caliber ammo listed.

Concrete (5,000 psi), 5.56: .5 inch, 7.62 and 30 cal, 7 inches.

Wet sand, 5.56: 25 inches, 7.62 and .30, 36 inches.

Packed or tamped earth, 5.56: 32 inches, 7.62 and .30: 48 inches.

Q. I heard that M855 has had serious stopping problems in Afghanistan, and earlier in Somalia. Is this true? It's possible, yes. Though early M855 experiments showed the round fragments well in the lab, more recent testing has been showing inconsistent fragmentation. Partially because of the complex construction of the round, M855 has widely-variable yaw performance, often not yawing at all through 7-8" or even 10" of tissue. Testing has shown large batch-to-batch differences in yaw performance even from the same manufacturer, and given the number of plants manufacturing SS-109-type bullets, fragmentation performance is very difficult to predict. This is complicated by the low velocity implicit in using M855 out of the short barreled M4 platform. Interesting, few of these reports seem to be coming from troops 20" or SAW platforms. It would seem that the additional velocity from the longer barrel provides adequate usable fragmentation range for M855 in the majority of cases. From shorter barrels, such as the M4's 14.5" barrel, M855's fragmentation range varies from as much as 90m to as little as 10m, which frequently isn't enough range. From Dr. Roberts: "Combat operations the past few months have again highlighted terminal performance deficiencies with 5.56x45mm 62 gr. M855 FMJ. These problems have primarily been manifested as inadequate incapacitation of enemy forces despite their being hit multiple times by M855 bullets. These failures appear to be associated with the bullets exiting the body of the enemy soldier without yawing or fragmenting. This failure to yaw and fragment can be caused by reduced impact velocities as when fired from short barrel weapons or when the range increases. It can also occur when the bullets pass through only minimal tissue, such as a limb or the chest of a thin, malnourished individual, as the bullet may exit the body before it has a chance to yaw and fragment. In addition, bullets of the SS109/M855 type are manufactured by many countries in numerous production plants. Although all SS109/M855 types must be 62 gr. FMJ bullets constructed with a steel penetrator in the nose, the composition, thickness, and relative weights of the jackets, penetrators, and cores are quite variable, as are the types and position of the cannelures. Because of the significant differences in construction between bullets within the SS109/M855 category, terminal performance is quite variablewith differences noted in yaw, fragmentation, and penetration depths. Luke Haags papers in the AFTE Journal (33(1):11-28, Winter 2001) describe this problem."

Opinion: It seems that several projects are in the works to review the use of M855 by the U.S. Military, and even replace the round in light of these terminal performance issues.

Q. Is military ammo the best choice for defensive use? M193 is probably the best choice for an all-around ammo selection, given its low price, wide availability, and the ability to be stabilized from any 5.56 rifle. For military-type operations, M193 should comprise the bulk of your 5.56mm ammo. However, other types of ammo may be better for a specific application, such as home defense or police work, or when using a 5.56mm gun with a very short barrel or when velocity is likely to be low. For police-type work where a soft-point is desired, Winchester 's 64 grain PowerPoint (in the Super-X line) and PowerPoint Plus (Supreme line) are top performers.* It has the advantage of being less sensitive to velocity by relying on bullet expansion rather than fragmentation, and is more consistent over a longer range of velocities. It would also be a better choice for use in AR-type pistols and short-barreled rifles, where the short barrels impart much lower velocities on the bullets. The downsides of this round are: questionable stability in 1:12 -twist rifles, a smaller wound channel compared to a fragmenting bullet, and a cost of 3-4 times as much as M193. *Note: Winchester offers a crimped version of this load in their LEO-only Ranger line. Stock number RA223T2. This load was selected as the standard duty load by the California Highway Patrol (CHP). Opinion: This question really comes down to how much ammo you want to purchase (cost) and how much faith you have in fragmentation (or which side of the fragmentation/controlled expansion argument you come down on). There are strong arguments on either side. The determining factor for you may be small. If you expect engagements inside your home, or under 50 meters, M193 and M855 will perform wonderfully for you. As ranges go out past 150 meters you may prefer heavier hollowpoint or softpoint rounds. The authors tend to prefer M193 over specialty rounds (with the exception of 77 grain Nosler NATO loadings for special home defense applications) and M855 because we believe it produces larger wound cavities and is more effective at likely defensive ranges (inside 150 meters), as well as easier and cheaper to buy in bulk-- making it cheaper to train with the ammo you use defensively. This is key, because no ammo is going to be effective if you cannot place shots on target.

Q. But what about specialty commercial rounds, like TAP, hollowpoints, and softpoints? Aren't they better than Mil-Spec ammo for defensive use? It really depends what you are looking for. In general Soft Point, Jacketed Soft Point and Jacketed HollowPoint rounds use controlled expansion as a wounding mechanism, rather than fragmentation. The yawing effect of FMJ bullets is frustrated by JSP and JHP rounds because the nose flattens down on impact (like a mushroom) and moves the center of gravity forward on the bullet. As a result, the bullet doesn't yaw, but instead gets its stability from the transfer of the center of gravity. Generally these rounds continue forward in tissue nose-first instead of trying to turn tail-first. Some very light JSP or JHP rounds will still fragment because their jackets are so thin and their velocity is much higher (up to 3800 fps in 40gr rounds), but this does not necessarily make their wounding capacity more dramatic than M193 or M855 primarily because their penetration depth is much lower. Hollow-point and ballistic-tip bullets are designed as varmint rounds, to expand quickly, making large, shallow wounds with relatively little penetration. These types of wounds aren't likely to take an attacker out of the fight immediately, especially if you have to shoot through an arm or from the side. Most experts agree that at least 12 inches of penetration is required to reliably reach the vital organs, and most varmint bullets won't penetrate more than 5 to 6 inches. Although some police departments use the Hornady TAP ("Tactical Application Police") round, which is merely a hotter-loaded V-Max varmint round, the primary motivation for adopting this ammo is preventing over-penetration of both bad guys and of interior walls. It should be noted that many of these concerns are proving unfounded as testing on interior penetration is increasingly showing that 5.56 rounds are less of a overpenetration risk than even the 9mm handgun ammo that many departments deploy in submachineguns for interior raids. The advantage of heavier (64, 69 and 69+ grain) JHP and JSP is that they will exhibit controlled expansion at slower velocities (and therefore have better wounding potential) than FMJ rounds at distance. This really starts to kick in after around 200 meters or so if you are dealing with a 20" barrel. After that distance, most rounds are below the 2500-2700 fragmentation threshold, and though FMJ rounds will tumble, it's not clear that this will be as effective as a good controlled expansion round. Lighter JSP and JHP rounds probably aren't as effective after passing through a soft medium, like an arm. In these cases FMJ will usually retain more penetration ability than the light JSP and JHP rounds. If you plan on using specialty rounds make sure to stick with heavier round. Some specialty rounds that have seen good results in gel, including penetration and fragmentation criteria, include: 64 gr Winchester PowerPoint (RA223T2).

68 gr Black Hills Match (Hornady bullet) (BTHP).

69 gr Sierra MatchKing loadings.

75 gr Hornady Match (BTHP)

75 gr Hornady TAP (BTHP)

77 gr Black Hills Sierra MatchKing (BTHP) In particular 70+ grain rounds often maintain their fragmentation properties far beyond the fragmentation range of M855 and M193.





50gr .223 Remington JSP in gelatin

Note the less dramatic fragmentation effects.

Counter Opinion: Specialty Rounds are the best choice for defensive use.

Specialty rounds have been gaining popularity among police and tactical teams and appear to perform very well. Consider the results of this shooting with Federal 55-grain HP: When the autopsy was performed, the forensic pathologist was amazed at the degree of internal devastation caused by the .223 round. There was a two-inch void of tissue in the chest, with a literal "snowstorm" of bullet fragments and secondary bone fragments throughout the upper left chest area. The round struck the subject 11 inches below the top of his head and inflicted the following wounds: Penetrated the top of the left lung, left carotid and subclavian arteries. The collar bone and first rib were broken. Cavity measured 5x6 centimeters. What is significant about this "instant one-shot stop" was that the round did not strike the subject at the most effective or optimum angle and did not involve any direct contact with the heart or central nervous system. .223 for CQB.





75 grain TAP in gelatin. Note that this TAP load uses the 75gr OTM bullet (not the A-Max) and that lighter TAP loads (40-60 grain) use the V-Max bullet and fail to meet penetration minimums.

Q. Won't JSP and JHP rounds be safer indoors? Don't I have to worry about FMJ rounds going through walls and hurting my family or others? You always have to worry about it, of course, but even FMJ 5.56 rounds will have less wound potential after penetrating a wall than even 9mm handgun rounds. Generally after passing through an interior wall or two, 5.56 bullets will have lost enough velocity that resulting wound damage would be greatly diminished. It should be noted, however, that all of the above bullets are still potentially deadly to those on the other side of a wall, so plan accordingly. Interior walls are concealment, NOT cover.



Fact: Evidence increasingly shows that 5.56 FMJ rounds like M193 and M855 are not the over-penetration risk they have often been though of as. In interior wall tests, 5.56 rounds have less wounding potential after wall strikes than any common 9mm or above handgun ammunition and/or 00 Buck shotgun loads.

Q. I'm concerned about roving packs of zombies driving automobiles after the end of the world as we know it. Since, as everyone knows, you have to make headshots to kill zombies, what ammo should I be using to defeat zombies in automobiles? Without commenting on the wisdom of engaging roving packs of zombies without adult supervision, the best performing rounds, in terms of penetration of 6mm laminated front windscreen auto glass and other automobile structures, are probably the Federal Tactical 55 and 62 grain bonded JSP (LE223T1 and LE223T3). Be aware, however, that these rounds, topped with Speer's Trophy Bonded Bear Claw bullet, are designed for penetration and generally do NOT fragment in CQB circumstances. Unfortunately, Federal Tactical ammo is LEO-only, and while the Trophy Bonded Bea