First Strike Test Series, Part 2: Action Type and Accuracy (closed vs open bolt)



Contents Intro and Manufacturing Consistency Action Type and Accuracy

The What, Why, and Before



Do the forces involved in a paintball markers internal firing cycle affect First Strike accuracy? We know that in the real steel world it does, in fact, make a difference. As a general holistic trend, the accuracy of a firearm scales with the magnitude of forces involved in it’s firing cycle. For example, compare the accuracy expected of a bolt-action sniper rifle to that of a sub-machine gun.



But in general paintball its been (rightly) accepted that these forces do not play a significant role in a marker’s accuracy. Paintball’s technical community has found that either the forces involved are too small to negatively affect the projectile or the inherent inaccuracy of a paintball is so great that any minor added error from forceful firing cycles is lost in practical testing. Either way, the end result is the same; it doesn't seem to matter what kind of marker you use. At least with conventional ammunition.



First Strikes are much much more accurate than classical spherical paintballs. It stands to reason then, that any added error from a forceful firing cycle has a greater chance of manifesting in a measurable way. The signal is much less likely to be lost in the ammo’s “noise”. Furthermore any additional error in FS accuracy will matter more than with classical ammo since the round itself and the playing style typical of shaped ammo is much more dependent on that accuracy for it’s kills (and cost-per-kill). With First Strikes it both easier and more critical to find out if there is any added error from the marker’s action.



Before we move on, lets make note of some technical considerations. First, the action is the mechanism by which a marker loads, fires, and recocks. Typically a marker loads a round from the open or closed bolt position, fires it with some variation of poppet or spool valve, and recocks in an autoloading capacity or manually. Open bolt guns feed, fire, and then recock in that order. Closed bolt guns fire, recock, and then feed. The advantage of which, at least in the real steel world, is that there is less potentially disruptive motion in the gun before the round is released. Poppet valves tend to accelerate rounds faster than spoolies (hence their efficiency) but are also known for the kick that this produces. Auto-loading (semi-automatic or automatic) guns likewise experience more movement when firing than manual/pump guns.



Secondly, 'force' in the preceding and the following, refers to the holistic forces experienced by a given marker during its firing cycle. Specifically, from the time that the trigger is pulled to the moment the round exits the muzzle. For example, in open bolt auto-loading guns this would mean the sum forces experienced by the gun during chambering, striking the valve, and the simultaneous acceleration of both the round and the action. Note that since action type is how we're measuring force in this experiment (lacking more sophisticated means), I sometimes use the terms interchangeably.



The Numbers



Da numbers.







Methodology and Interpretation



With the previously discussed action types there are eight possible configurations of marker. For practical reasons not every variation was tested since some configurations are difficult to acquire, redundant in terms of the forces they experience, and/or less applicable to the paintball community as a whole. Instead, three marker configurations were used to bracket the range of forces from highest, to middling, to least. For the highest force, we fired an old school Spyder - an open bolt semi-auto poppet. For the middling force we used the data produced by



Note that the Punkworks results are qualified with an equal to or greater than symbol. The limitations of their firing platform resulted in shifting points of aim for each eight round magazine. These groups were then mathematically corrected and centered on the same point. The math used to do this, however, can damp out some of the natural randomness in the rounds. Generally, the larger the dispersion the more exaggerated the improvement. In small dispersions the improvement is minor or non-existent. Since the final value is relatively small, I’m confident that it’s close to what the value would have been, had their magazine not forced a shift in the point of aim. If anyone is interested in the specifics of the math I’ll post up some previous testing runs and walk through the proof for the above generality.



The test was conducted in an indoor un-airconditioned range. Specifically, the newly acquired first floor warehouse of the local hacker/maker space



For the open bolt poppet and the closed bolt poppet (the Spyder and Trracer respectively) each round was loaded into the breech and pushed forward past the breech by hand. This was done for two practical reasons, the markers did not have magazines that could feed rounds into them, and more importantly, it prevented the bolts from damaging the skirts and influencing accuracy. The Spyder MR5 (a mag fed gun) we used earlier in testing would occasionally do this; though, since we were using an early run barrel adapter, I cant say that it was due to a design flaw in the MR5 itself.



A laser was mounted to each marker and projected onto the wall behind the target. A mark was then taped to the wall to indicate the original point of aim of the marker. The mark and laser point were compared after firing to ensure that they occupied the same point. Since any shift in the markers orientation during firing would cause the laser to move off the reference point, by doing this, we were able to ensure that the point of aim remained constant throughout firing.



As for the accuracy metric (the means by which we measure accuracy), I've included both x-component standard deviation and vectors. If you’re unfamiliar with those terms, the x-component refers to the amount of left-right dispersion that a given group suffers from, and standard deviation is a statistical method for measuring how wide that dispersion is. If that didn't help much, here's a link that explains



Hammerhead rifled barrels were used for each test. The high and low force markers used the exact same barrel, and the medium force marker used a model specifically designed for the T9. The key barrel specs in each case are the same: 0.688 bore and a 1:52 twist rate. A semi-formal data driven analysis of paintball’s leading shaped projectile. I know its been awhile since my last test release but there were some trials and tribulations between here and there, check out the link if you're interested in the meta-process that goes into ensuring quality data.Do the forces involved in a paintball markers internal firing cycle affect First Strike accuracy? We know that in the real steel world it does, in fact, make a difference. As a general holistic trend, the accuracy of a firearm scales with the magnitude of forces involved in it’s firing cycle. For example, compare the accuracy expected of a bolt-action sniper rifle to that of a sub-machine gun.But in general paintball its been (rightly) accepted that these forces do not play a significant role in a marker’s accuracy. Paintball’s technical community has found that either the forces involved are too small to negatively affect the projectile or the inherent inaccuracy of a paintball is so great that any minor added error from forceful firing cycles is lost in practical testing. Either way, the end result is the same; it doesn't seem to matter what kind of marker you use. At least with conventional ammunition.First Strikes are much much more accurate than classical spherical paintballs. It stands to reason then, that any added error from a forceful firing cycle has a greater chance of manifesting in a measurable way. The signal is much less likely to be lost in the ammo’s “noise”. Furthermore any additional error in FS accuracy will matter more than with classical ammo since the round itself and the playing style typical of shaped ammo is much more dependent on that accuracy for it’s kills (and cost-per-kill). With First Strikes it both easier and more critical to find out if there is any added error from the marker’s action.Before we move on, lets make note of some technical considerations. First, the action is the mechanism by which a marker loads, fires, and recocks. Typically a marker loads a round from the open or closed bolt position, fires it with some variation of poppet or spool valve, and recocks in an autoloading capacity or manually. Open bolt guns feed, fire, and then recock in that order. Closed bolt guns fire, recock, and then feed. The advantage of which, at least in the real steel world, is that there is less potentially disruptive motion in the gun before the round is released. Poppet valves tend to accelerate rounds faster than spoolies (hence their efficiency) but are also known for the kick that this produces. Auto-loading (semi-automatic or automatic) guns likewise experience more movement when firing than manual/pump guns.Secondly, 'force' in the preceding and the following, refers to the holistic forces experienced by a given marker during its firing cycle. Specifically, from the time that the trigger is pulled to the moment the round exits the muzzle. For example, in open bolt auto-loading guns this would mean the sum forces experienced by the gun during chambering, striking the valve, and the simultaneous acceleration of both the round and the action. Note that since action type is how we're measuring force in this experiment (lacking more sophisticated means), I sometimes use the terms interchangeably.With the previously discussed action types there are eight possible configurations of marker. For practical reasons not every variation was tested since some configurations are difficult to acquire, redundant in terms of the forces they experience, and/or less applicable to the paintball community as a whole. Instead, three marker configurations were used to bracket the range of forces from highest, to middling, to least. For the highest force, we fired an old school Spyder - an open bolt semi-auto poppet. For the middling force we used the data produced by Punkworks in their FS rifled barrel test for the Tiberius T9, an open bolt semi-auto spoolie. For the lowest force we used a closed bolt pump spoolie in the form of an Empire Trracer that was graciously provided by scotallen1986 for use in this test series.Note that the Punkworks results are qualified with an equal to or greater than symbol. The limitations of their firing platform resulted in shifting points of aim for each eight round magazine. These groups were then mathematically corrected and centered on the same point. The math used to do this, however, can damp out some of the natural randomness in the rounds. Generally, the larger the dispersion the more exaggerated the improvement. In small dispersions the improvement is minor or non-existent. Since the final value is relatively small, I’m confident that it’s close to what the value would have been, had their magazine not forced a shift in the point of aim. If anyone is interested in the specifics of the math I’ll post up some previous testing runs and walk through the proof for the above generality.The test was conducted in an indoor un-airconditioned range. Specifically, the newly acquired first floor warehouse of the local hacker/maker space JaxHax . The distance from gun to target was 75 feet and the gun was clamped firmly by the firing table. Our rounds were ratioed according to the average size distribution found in the Manufacturing Consistency test and both the Spyder and the Trracer were regulated by a Palmer's Stabilzer. The impacts were recorded on a 1” x 1” grid so the final position of the hits were rounded to the nearest whole number, unless they fell directly between two grid lines in which case they were recorded at the half simply because I didn't like the existential dilemma of having to round a perfect split. Previously, we’ve run tests down to a resolution of 0.1 inches but as it turned out, that amount of accuracy did not produce different final results from a 1 inch resolution - it was also a massive pain in the ***.For the open bolt poppet and the closed bolt poppet (the Spyder and Trracer respectively) each round was loaded into the breech and pushed forward past the breech by hand. This was done for two practical reasons, the markers did not have magazines that could feed rounds into them, and more importantly, it prevented the bolts from damaging the skirts and influencing accuracy. The Spyder MR5 (a mag fed gun) we used earlier in testing would occasionally do this; though, since we were using an early run barrel adapter, I cant say that it was due to a design flaw in the MR5 itself.A laser was mounted to each marker and projected onto the wall behind the target. A mark was then taped to the wall to indicate the original point of aim of the marker. The mark and laser point were compared after firing to ensure that they occupied the same point. Since any shift in the markers orientation during firing would cause the laser to move off the reference point, by doing this, we were able to ensure that the point of aim remained constant throughout firing.As for the accuracy metric (the means by which we measure accuracy), I've included both x-component standard deviation and vectors. If you’re unfamiliar with those terms, the x-component refers to the amount of left-right dispersion that a given group suffers from, and standard deviation is a statistical method for measuring how wide that dispersion is. If that didn't help much, here's a link that explains standard deviation . Vector is the most popular method for measuring accuracy in paintball. It combines the x and y component standard deviations into a single radius that can be used to model accuracy as a circle, similar to how some first person shooters model the accuracy of different in-game guns. If that didn't help, heres a link that explains vector in more detail . Personally, for reasons explained here , I prefer using the X-component standard deviation.Hammerhead rifled barrels were used for each test. The high and low force markers used the exact same barrel, and the medium force marker used a model specifically designed for the T9. The key barrel specs in each case are the same: 0.688 bore and a 1:52 twist rate. Last edited by Whiskey Hammer : 09-30-2014 at 12:40 PM .