I used to work at Barret Firearms, so lots and lots of .50BMG off the shoulder. I've shot as many as 15 rifles in an afternoon for score before they were packed up and delivered to the Army, 10 rounds apiece. This may not sound like much, but all the shooting was done laying on a concrete floor, with the barrel protruding through two sets of doors. The muzzle blast, even with the door set-up, was ridiculous.

I did my best shooting with their worst rifle, an M95. A bullpup design, 5rd mag-fed, obnoxious piece of dung.... I put eight rounds in one ragged hole before my nerves gave out and I started throwing "flinchies" everywhere. The cocking handle lay approx. 1" from my larynx, as I shoot left-handed, and bumped my throat during recoil every shot.