outside dim of .308 and 7.62x51 are identical, military cases are smaller inside due to a thicker case. this is because some machine guns ( military does not have a different ammo for machine guns) are fired from open bolt position (this allows for higher cyclic rates). so with that said most reloading data will spec 10% less for starting loads . I learned this the hard way, my reloads shot well in M1A with 42 gr of IMR but in a bolt gun the cases split the same way. I now load specific to bolt or gas guns. your friend google can shed some light on LC brass. Hope this helps. I know its an older thread.
