Obviously the American designers of the M3 borrowed from STEN gun ideas but came up with a less sturdy, collapsible buttstock and an odd cocking handle on the right side behind the ejection port. Odd because it’s a fragile arrangement and was dispensed with in the M3A1 version. Here’s something else odd about M3’s: They could be converted from .45 ACP to 9mm merely by switching the bolt and barrel and installing a magazine adaptor for STEN gun magazines. (I’d love to find one of those conversion kits for my “grease gun.”) Rate of fire is the slowest of all WWII submachine guns at 450 RPM and mode of fire was full-auto only.

Now I’m going to detail some personal opinions based on my experiences with these subguns. However, I urge the reader to keep in mind I am not a submachine gun expert and have never been trained in their use.

Here goes: In my opinion the double-stack, double-feed magazine of Tommy guns is a far better system than the double-stack, single-feed methods used in the other four subguns. Not only is my Thompson more reliable in terms of function than the others, but also no special magazine loading tool is needed for it. The M3 grease gun is the second most reliable subgun in my collection, followed by the Soviet PPSh41. Both German MP40 and STEN Mk II fail to function far more than the others.

As regards to disassembly for cleaning, top honor goes to the PPSh41 with the MP40 and STEN Mk II tying for second place. Both American subguns are more time-consuming to tear down for cleaning. Thompson and PPSh41 barrels are fixed in the frames so they must be cleaned from their muzzle end. The others’ barrels can be dismounted and cleaned from the breech end.

Three of my five subguns offer semi-auto fire on demand. The US M3 grease gun and German MP40 do not. Is that a detriment? I don’t think so because in my life-long extensive study of WWII history, never have I encountered a first-person story of a combatant from any nation firing his submachine gun on semi-auto. You might think more precise bullet placement would come with semi-auto, but all five of the subguns discussed here fire with an open bolt. That heavy chunk of steel sliding forward for the first shot does nothing to aid well-aimed shots.