This is a one of kind machine gun ! Its a DEMRO WASP mfg in Connecticut ! We have never had one of these in 25 years, let alone a factory machine gun ! This is not a conversion ! The receiver says 45 acp or 9mm, but this one is in 9mm. It takes unmodified STEN mags. This is the for the discerning collector of one-of-a-kind machine guns.