UMP actually fires a larger round then the 74u.
.45 caliber bullets coming out of an SMG in close quarters would be scary as fuck. Although 9mm rounds coming out of an SMG are scary as fuck in real life.
Anyway point is the 74u doesn't fire the large 7.65mm round an AK-47 does.
You are mostly right.
I was in the Army though. Firing a 240 bravo vs an M16 you can absolutely see and feel the difference between the rounds you are firing.
I've never been on the other end of it though so I couldn't really tell you one way or another.