 Compared to more modern submachine guns, the Thompson is quite heavy, weighing roughly the same as the contemporary M1 Garand semi-automatic rifle, and requires a lot of cleaning.This was one of the major complaints about the weapon by U.S. Army personnel to whom it was issued.Although the drum magazine provided significant firepower, in military service it was found to be overly heavy and bulky, especially when slung on the shoulder while marching.