That is assuming one is stupid enough to try and rob someone who owns and most likely really likes to shoot machine guns.
That was tried about a decade back in Indianapolis, by a street punk armed with a knife, who broke into the business adjoining an Indy gun shop, waited for the owner to close up, then cut through the intervening wall, bypassing the roof/door/window alarm systems.
Surprise, surprise: the owner was still inside, having let an after-hours visitor leave. And he had his suppressed H&K MP5SD smg in hand. When told to drop the knife, the felon did not, and the shooter let fly. And missed with all 30.
And so he went to his backup plan: another MP5 family buzzgun, unsuppressed this time, and let go anmother magazine's worth. One round hit the assailant and killed him; 14 years old, as I recall.
I think the shop owner would have been *much* better served with a shotgun, but inside his store without hearing protection, and at night, maybe not- particularly if there was more than one *visitor* involved. No criminal charges, and a *no bill* from the grand jury shortly thereafter. If imperfect, not nearly as bad an outcome as might have been.
60 rounds for one fatal hit. Not good odds if you ask me.
L