Sadly, this is a square peg round hole problem. The AR-10/LR-308 platforms are classified as service rifles. They were made for the 7.62x51 cartridge. .308 win commercial ammunition is loaded to higher pressures for bolt action rifles. The 7.62x51 has a sloppier chamber, so the wall thickness of the brass is thicker to keep the brass from splitting. Thicker wall brass means less powder, which means lower pressure. This allows service rifles to cycle and extract faster, while the brass is still expanded, even when the chambers are hot. The tighter tolerances of the bolt action rifles allows for thinner walled cases so more powder. No one is going to cycle a bolt gun fast enough to see the problems that the service rifles will see.
Sadly, there are only a few ways to cure this. One: Go to a high pressure bolt. Many of the bolt manufacturers are running with too much clearance around their firing pins which allows primer flow and holes in primers or even popped primers. I use a Rubber City Armory bolt.
Two: Lower pressure ammunition. In my personal .308 I have found that certain brands are just too hot. I tried some Winchester 150gr Deer XP's and had the same issues as described above, brass swiping, popped primers, holes in primers, etc. But I do not have the same problems with Hornady 150gr SP's. I have never had a problem with mil surplus ammo in 7.62x51. Nor have I had problems with heavier bullets. Heavier bullets mean less powder which means less pressure and less problems.
It may not sound like a good way to fix things, but it is just what we have to do to get them to work right, unless the ammunition manufacturers catch on and start loading service rifle specific ammunition.
Adjustable gas blocks won't solve this problem. They are used to fine tune the cycling through gas control, not to control overpressure of the ammunition.
Just my observations from working with customers rifles over the years.
