How about the M1A1 version of the Thompson that Savage Arms made during WWII? They simplified the thing by getting rid of the Blish Locking System and making it a straight blowback operation. They also got rid of the Cutts Compensator and the drum magazines. You can tell them from the traditional versions because they have the cocking handle on the side rather than the top. A friend picked one up in the Cholon district of Saigon, now Ho Chi Minh City back during the VietNam War. He was assigned to the Riverine Forces down in the Mekong Delta and wanted something firing a heavy slug for brush busting. He loved the thing, saying that it was like a Model 1911A1 in that it just chewed up dirt and kept right on firing.