Originally Posted by kc
I was thinking of the recoil damaging the AR in the long run from using the calibre.
You don't have to worry about that since an AR-15 can't handle 308 rounds though it's magazine. They way too long. The AR-10s are plently strong for a a 308 Win with larger and heavier bolts and locking lugs. They're even chambered in 300 SAUM and strong enough for them.
There's also the Olympic 300 OSSM which is a 25 WSSM necked up to 30 caliber and works in an AR-15 upper. It's bolt and barrrel extension are heavier to to take the higher pressure and larger size than other AR-15s, but it too is stronge enough and gives nearly identical performance to a 308 when shooting 150 grain bullets (same as military ball ammo)
AR-15 stocks and receivers are much more likely to be damaged by rough handing like dropping them onto rocks than from recoil. The only parts under pressure from the propellent are the barrrel, barrel extension, and the bolt. The locking lugs are the weak part on mil-spec AR-15s, but plently for 5.56x45 and lower pressure rounds like the 50 Beowulf and 458 SOCOM.