AMT made an auto called the Javelina (don't know if the spelling is correct) that fired the M1 carbine cartridge. Haven't seen one in years. At an indoor range many years ago and the guy in the next both was shooting one. Man was it loud. He really like the gun though. But dropping the gun from a 16inch rifle barrel will probably really effect velocity. Plus ammo has gotten real expensive for them. Not like when all the old military stuff was floating around years ago.