The submachine guns being used by most of the Dirty Dozen is the M3, .45 caliber ACP submachine gun known as the "Grease Gun". It came into use late in the war, replacing Thompson submachine guns (Tommy guns). It was not a general issue weapon to infantrymen, but normally used as the crew weapon on a tank. Many "found" their way to the frontline troops, however. This earlier model weapon had a charging lever on the side. Later models (M3A1) were charged by simply pulling back on the bolt by inserting your finger into a recess in the bolt. The M3A1 wire stock included a tab to help load magazines, the ends threaded to accept a cleaning brush to clean the barrel, and was used as a wrench to unscrew the barrel for disassembly. The weapon, only manufactured during World War II by General Motors Headlight division, cost about twenty dollars to produce, as opposed to the Thompson, which cost several hundred.