07-16-2021, 06:33 PM
Old Bob Wrote:Y'all have brought up a problem I might have never considered in my 6 AR rifles. It turns out - after checking - that none of my rifle's BCG gas keys are striking the back of my lower receivers. I measured the gaps between my lower receivers & fully inserted BCGs: .141" to .169". The .141" is with a JP buffer spring assembly; the rest of my ARs have David Tubb springs.
So, if a BCG is hammering the back of a lower receiver, it's caused by an out-of-spec buffer tube/too short recoil spring? Eh? How common is this?
It is more common than many realize.. A bolt carrier that is shorter than 6.700 in length can also cause this problem, with everything else near or under spec...This can also fall under the stacking tolerance issue...