I've owned two AM180s and while they are fun for a line shoot, I think they're a little delicate and finnicky for serious work. Let me clear up a few misconceptions about them though:
Contrary to what you may think, just because they shot .22 doesn't mean they are cheap to shoot. The cyclic rate averages between 27-30rds/sec, so you can easily cburn through several thousand rounds in an afternoon. I was buying Federal Lightnings by the 5000rd case (about $125 delivered) and a single case would last 1-2 shooting sessions. Just think, the largest drum holds more than half a brick of .22 ammo (275rds), and that only takes about 9-10 seconds to unload.
Since the selector pins on AM180s have a tendency to break more often if you stop firing in the middle of a drum, the more you stop, the more spares you'll need (at about $10/each). Of course if you don't stop, you just burn through ammo more quickly. If you do stop in the middle of a drum, the guns also have a tendency to keep going for a few rounds (and at that speed, its usually more than just a 'few'). They just don't like the stop-start-stop-start action.
The Utah Dept. of Corrections is the only LE agency that has ever officially used them, however, the Yugoslavian MGV-176 is virtually the same gun.
The drums come in four flavors - metal 165rd, lexan 177, lexan 220, lexan 275 and is driven by a flat coil spring in a winder that sits in the drum. Yes, before you shoot you have to wind up the gun like some sort of toy...
Jams happen and can often take several minutes to clear. When they run, they're great; when they don't they are the most frustrating thing ever.