Ian’s vide on the M55 and on the M50 on which it was based.

Reisings were designed and produced by Harrington & Richardson (H&R) Arms Company. The design is closed bolt, which makes it different from the more commonly known Thompson and Grease Gun SMGs which fired from an open bolt. Like those other guns, the Reising was chambered in .45 ACP. It had a cyclic rate of fire of around 500 rounds per minute which put it between the fire rates of the Thompson and Grease Gun.

The M55 variation on the original M50 design was shortened by replacing the original wood buttstock with a folding metal wire stock. Otherwise the other noticable difference was the removal of the M50’s compensator, leaving the M55 with a simplified muzzle.

The Reisings were produced beginning in 1941, but withdrawn from frontline service in 1943, following complaints about reliability. Despite this, the guns saw were ordered from H&R by US law enforcement into the 1950s.