I thought a 50 beowolf could fit on a multi cal which would require a larger mag well than a 308, right?
Nope the Beowulf fits a standard M4 or AR15 lower. Also I see several posts in this thread refering to Long action. While the AR10 is longer and larger than the AR15 the AR10 is chambered for what are considered short action calibers when talking other gun types ie bolt or lever. The AR10 is designed around the 7.62 Nato (308 Winchester) cartridge and can be found with barrels for some of the other 308 family of cartridges that share the same case but different bullet diameters like 243, 260, 7mm-08, 308 and 338 Federal plus some others of the same overall legnth.