I only have experience with the MAC-10. As others have mentioned, the open bolt and crude sights don't make it easy. Here are my results -
Using GI ball equivalent at 10-15 yards on a standard police silhouette, firing a three round burst. POA was at the knees. The first round hit at POA, the second round at waist level, and the third around the head or the neck. Admittedly, my technique could probably stand some improvement, but that was my experience.
Using the same ammo on semi-auto was a different story. Shot well, and it was even possible to connect at 200 yards on small targets, once the holdover was determined.
The real revelation was when we switched to using handloaded ammo with 200 grain LSWC at around 720fps. This was just strong enough to cycle the bolt. A couple of times we had runaways, so just a little bit more velocity would have made the difference. On full auto, no problem keeping three or four round bursts at 10-15 yards within a five inch circle. The gun really settled down, and showed what it could do with ammo more suitable for something so short.
YMMV and FWIW,
emc