This is the Thompson .45 caliber submachine gun from WW2 and the Korean War.
It is not exactly to scale, but approximates the M1A1 in important respects. I opted for a vertical grip - instead of an angled one like the real M1A1 - so that a minifig could grip it. If it angled back, I wouldn't have been able to add the trademark curved shoulder stock under the receiver.
If the stock were any longer, a minifig could not hold it.
I designed it in a CAD program, and had an ABS plastic injection mold made. The mold can produce these in ABS plastic - just like Lego does.
HEY WILL! I didn't know you had a MOCPAGES site! Oh, and I finished your Brickarms movie. I just got a MXL 990 Mic and still need to do the voices. I'f you'd like to see some of my creations, you can click on the link above. And this is a awesome Thompson I own about 10 of them and use them all the time! Luke