I was looking through the study and another thing I noticed that would make it impossible to get valid results in relation to accuracy is the tool itself they use to measure the gas pressures. It would greatly affect the harmonics of the barrel and skew any result. The crown they use is also not a target crown or anything of note which would help determine proper accuracy which is understandable as I imagine they were trying to get the study done quickly with the same atmospheric conditions and taking the time to try and turn a nicer crown every time would be exhausting.

Above all though one thing really stood out which many will not notice, but as I've seen the argument laid out time and time again where people think a longer barrel equates to more velocity...



The reason I bring this up is it's been argued by men who know more about this than I will likely ever know, but when it comes to semi-auto platforms there is no need for a barrel beyond 23" even if you're using a hotter cartridge like the 6mm CM on a large frame. This is due to the fact that it is a gas operated system which has pressure limits less than a bolt there are no advantages to a long 24"+ barrel. Most calibers in barrels on semis <23" will give you the maximum available velocity, and with an appropriate twist stabilization of even the heavier rounds even beyond the point of a round going transonic. I know it's a sidetrack from the topics real focus, but it's a good point that can be observed within the test itself although unintended by the author.