Standard 308 ammo for snipers is Federal Match grade manufactured with the Sierra 168 HPBT Match King bullet. In fact, if you go to FBI sniper school at Quantico, they used to provide you with a CASE of it all from one lot.
Now, I have some SEAL sniper ammo that is 300 Winchester Magnum. It is NOT "factory loaded". It is pretty much ballistically equivalent to my own very fast hot loaded ammo. What I have is the same Sierra 168 grain HPBT Match King above, over a max ( I WILL NOT reveal what the charge is) charge of 4350 with a large rifle magnum primer. In MY Winchester Model 70 with a 26" barrel, it clocks right at 3300 fps. The SEAL ammo shoots to within about 1/2" or so of the point of impact of my ammo.
The 300 Winchester Magnum ammo used by the rifle teams is also custom handloaded.
The Barrett also gets a special diet, as opposed to getting the standard ammo issued for the Ma Deuce.
Were I going to battle, I'd MUCH prefer an M1 Garand or an M14, with a 1911, to the current M-16 variant and the Beretta. I'll pass on the 5.56 and 9 stuff, thanks. I use .22 caliber stuff for varmints. Granted, my old Model 70 220 Swift was deadly accurate, and hit hard, but not like my 300 Winchester, 30-06, or my shooting buddy's various 308s, including an AR variant chambered for 308.