UOP said it delivered these trial guns in a carbine configuration, known specifically as the M4-WAC-47. These weapons appeared to have 16-inch long barrels, though, unlike the 14.5-inch barrels on standard U.S. military M4s . The trade-off is always that a weapon with a shorter barrel might be handier, particularly for troops who have to get in and out of aircraft and other vehicles or otherwise operate in confined spaces, but it will also be less accurate, especially at longer ranges.

“The first batch of WAC-47 … will go into trial operation in the combat units of Ukrainian army,” UOP said in an earlier press release about the project in October 2017. “Gathering feedback from Ukrainian soldiers will enhance necessary changes before mass production starts.”

In a New Year’s statement on Jan. 3, 2018, Ukraine’s central state arms company, UkrOboronProm, or UOP, announced it had delivered the initial batch of WAC-47s to unspecified units by way of American firm Aeroscraft . Ukrainian officials first revealed plans to purchase the rifles in January 2017 and the country expects to eventually issue the guns across both its active and reserve military units and to personnel in other state security services. It would be an important upgrade for these organizations, which use dated variants of the legendary Kalashnikov AKM pattern as their primary service rifles at present.

The Ukrainian military has received the first of its new US-made WAC-47 rifles, a derivative of the American-designed M16 rifle that chambers the Soviet-era 7.62x39mm cartridge. Ukraine is primarily looking to get the guns as part of a push to modernize its forces and to make it easier for its troops to work together with foreign units , especially members of the NATO alliance, but in doing so they're also sending a clear political message to Russia.

The guns do appear to share the same basic operating mechanism as their American cousins, though. This so-called “direct impingement” system siphons propellant gas from the barrel as the gun fires to directly cycle the action. Both the AKMs and some newer derivatives of the M16 pattern use a physical piston, which helps keep particulate matter from building up on critical components and causing the weapon to jam. As such, the new M4-WAC-47s weapons will require more cleaning and routine maintenance than Ukrainian troops are likely used to with the notably simpler AKM-pattern guns. This will almost certainly require changes in training regimens and standard operating procedures to make sure Ukrainian troops take care of the new guns properly. A lack of understanding about the M16's cleaning and maintenance requirements, coupled with inaccurate sales pitches, poor quality control, and a change in the formulation of the gunpowder inside the cartridges, turned into an infamous scandal when U.S. troops in Vietnam first began to receive significant quantities of the rifles in the 1960s. The M4-WAC-47s also have the same style of controls, such as the charging handle, fire selector, and magazine release, as M16 pattern firearms. Photos of the prototype rifles show them with handguards featuring both U.S. military standard accessory rails and additional attachment points using American manufacturer Magpul’s M-LOK system. The rifles also had pistol grips and retractable buttstocks from Magpul.

Ukraine MoD A Ukrainian soldier poses with an AKMS rifle, the a version of the standard AKM with a folding stock.

Older AKM-based designs have notably limited space for installing similar systems so a user can rapidly attach grenade launchers, optics, laser aiming devices, flashlights, and other accessories. As such, the M4-WAC-47 could quickly offer Ukrainian troops additional capabilities with a minimum of effort, but only as long as the government in Kiev also purchases sufficient numbers of those ancillary systems. The most significant feature, though, is that the M4-WAC-47 uses the aforementioned 7.62x39mm cartridge. Most military M16 pattern weapons typically chamber the smaller 5.56x45mm round.

UkrOboronProm A M4-WAC-47 with a non-magnifying optic and a 40mm grenade launcher.

That’s not to say this type of caliber conversion – which can be as simple as adding a new barrel, bolt and carrier assembly, and magazine – is new. The ubiquity of the Soviet-developed cartridge, its heavier bullet, and the popularity of the M16 pattern design have long made the idea of such a combination attractive, particularly to civilian shooters. In the early 2000s, U.S. Special Operations Command (SOCOM) also expressed an interest in the idea. The underlying concept was that American special operators might end up conducting extended missions in areas with limited support where it might be easier to source 7.62x39mm ammunition. It would also improve their ability to work closely with local forces armed with AKMs or other similar guns chambered in that round, something American special operators had done extensively in the opening phases of the war in Afghanistan. Since the Vietnam War, special operations forces, advisers, and even regular troops have often just carried AK type rifles they had captured or otherwise acquired for a variety of reasons, too. SOCOM subsequently crafted a requirement for a weapon that its personnel could easily convert from one caliber to another, known as the Special Operations Forces Combat Rifle, or SCR. One of the firms who submitted designs was Knight's Armament Company, which crafted an M4 carbine derivative known as the SR-47, which not only used the larger cartridge, but would accept standard AKM magazines.

Knight's Armament Company The Knight's Armament Company SR-47.