Several years ago I had the chance to fire a privately owned MP40 at an indoor range (back then it could be done legally) and after a few hundred rounds, it did not misfeed once.I have fired and watched being fired many full magazines from a MP-40 and only remember seeing two failures to fire. One was a dud 1943 STEN round and the other just didn't feed. The bolt stuck half way but that was understandable since the gun had not been fired in over 30 years and there was a build up of metal oxide on the bolt. A little rubbing with fine steel wool and a light oiling of the side of the bolt fixed the feed issue.
If you spent a bit more time with an open bolt SMG you would notice the back and forth recoil impulse that all open bolt SMG's have. 9mm guns cycle fairly quickly so the dual impulse is not so noticeable. I have an M3 Grease Gun and it is really noticeable on that thing as the bolt weighs 2 pounds.With the firing from the open bolt design I thought you would feel a heavy bolt slap upon pulling the trigger which I did not notice at all.




























