|Feed||multi-layerpan magazine, 150 rounds|
|Rate of fire||750 rounds perminute|
The MAC M 1931 tank machine gun was developed by state Frencharsenal at Chatellerault. It was based on MAC M1924/29 light machine gun, and intended for use in Frenchtanks and armored cars, and also in fortess mountings in Maginot line.After the WW2, few M1931 machine guns were bought by Swiss army and after re-barreling to Swiss 7.5×55 GP11 cartridge, installed on certainSwiss tanks. Some other guns in French service during late 1940s were converted to ground role, with adoption of the side-mounted 35-roundbox magazines and adapters for US M2 tripods.
The MAC M 1931 tank machine gun is a gas operated weapon which fires from open bolt and in full automatic mode only. The long stroke gas piston is located below the barrel, and it operates the vertically tilting bolt group. Massive barrel cannot be removed and replaced in the field. Feed is from massive, multi-layer pan magazines that hold150 rounds of ammunition (with bullets pointing to the center of the round magazine). Depending on the version, magazine can be installed on right or left side of the gun, in vertical plane. Ejection is straight down, through the short chute attached to the base of the receiver.Firing controls include a pistol grip with prominent front-curverdshape, and a rifle-type trigger. Normally, a metallic shoulder rest is attached directly to the receiver.