I once had the extreme pleasure of emptying a full drum through an American 180. A suppressed American 180, in fact. Oh. My. Gawd. What fun!! Basically the only noise you could hear was the clatter of the bolt flying back and forth, and the tinkle of the brass hitting the ground. As I recall, we calculated that the slugs were going down range somewhere between 6 and 8 feet apart.
The gent who owned it (he also had an M16, a Sten and a couple of other cool toys I didn't get to shoot) said it was great for foxes on his farm. Said they usually got after his chickens in pairs, and with the suppressor he could drop one without spooking the second, and get them both. All I know is, 150+ rounds of .22LR goodness made a nice little dust cloud on the 100 yard berm, and I was smilin' for a couple of days. Hadn't had quite that much fun since walking the M60 across targets at 1000 meters.