For consideration:
A LOT of shooters believe their AR’s have “loose chambers,” because of how big their brass comes out after firing, completely unaware of WHY their brass is expanding so much. Commercial AR’s are notoriously over gassed to ensure feeding reliability, but this tends to mean the action is unlocking while the bore and chamber are still under excessive pressure, so we see a LOT of case stretch. It’s pretty common to see fired brass fit back into a bolt gun, but rather rare to see that happen for AR’s - the chambers aren’t stretching, the chambers aren’t loose, it’s just that the cases are getting blown out while the bolt is in motion, resulting in additional stretch, both in base diameter and shoulder length. Tune down your gas flow and you’ll see that symptom subside, and brass lasts much, much longer.
I agree, over gassing is a problem.
Gene Barnett used a commercial drill one size larger than the GI ports on his M1 and M1a match barrels. I assume the GI gas port drills were custom made to the needs of the pressure curve, not based on the inventory of Tool World. The Wilson match M1 barrel I have, the gas port hole is much larger than GI, and it recoiled so violently, I took it off. When I "gauged" GI M1 barrels and compared the holes to the Wilson match, the GI were smaller. And the existing gas port holes on GI M1 barrels were smaller than the "in print" dimensions which claim to be Mil Spec.
And it is not as if GI rifles were over gassed to begin with.
A custom barrel maker and gunsmith told me Kreiger replacement barrels for the M1 and M1a were cut with a reamer that left a large head. His opinion why this was the situation, was so future customers would not call up and complain to Kreiger about their new barrels not chambering their old reloads.
For decades in print writers have been claiming small base dies were not needed for the M1a, M1 Garand, etc. Gunwriter Mike Venturino was one. For decades he had been writing in print that only standard sizing dies are need. But in the July 2012 issue of Guns Magazine, he was testing an M1a and a AR10 and his reloads were too tight. I found it humorous to read that he had to beat the bolts open with scrape lumber. Ha, Ha.
At least Mike Venturino changed his tune, now he recommends small base dies for M1's, M1a's.
I will say, my Ruger Tactical M77 in 308 Win, the chamber mouth is extraordinarily large. Cases neck expand a lot. This is one of those hammer forged barrels, is very accurate, and that large chamber mouth will crack brass. I am sure Ruger did this on purpose so no one's ammunition is pinched in the throat.
The thing is, with gas guns, the reloader will learn that gas guns require much more attention to reloading than bolt guns. Reloaders get used to beating the bolt closed on their bolt gun, stuffing any old powder in the case, any old bullet, and any old primer, and that sort of stuff will jam a semi auto.
And, everyone is surprised when a sensitive "match" primer slamfires in their gas gun. Been decades of denial on that. Federals were the most slamfiring primer in M1's and M1a's. I collected slamfire reports on all military semi auto's, and with the exception of the roller bolts, all of them have in battery, and some out of battery, slamfire accounts with factory ammunition. And it is all due to free floating firing pins hitting sensitive primers during chambering.
The G3 roller bolt mechanism uses a firing pin spring that is very strong, and does not leave a dent on the primer of a chambered round.
I sent this M1 bolt to Roland Beaver for modification to reduce the impact energy of the firing pin on the primer.
and it still does this
I wonder why that primer did not ignite.
And yet there are those who deny that primers will go off due to firing pin inertia!
