TCM-20

The M45 Quadmount (nicknamed the "meat chopper" and "Krautmower" for its high rate of fire) was a weapon mounting consisting of four of the "HB", or "heavy barrel" .50 caliber M2 Browning machine guns (of the M2 Turret Type (TT) variant) mounted in pairs on each side of an open, electrically powered turret. It was developed by the W. L. Maxson Corporation to replace the earlier M33 twin mount (also from Maxson). Although designed as an anti-aircraft weapon, it was also used against ground targets. Introduced in 1943 during World War II, it remained in US service as late as the Vietnam War.

In order to develop a mobile anti-aircraft weapon, several 0.5 inch (12.7 mm) twin machine gun mounts were tested on the chassis of the M2 half-track including Bendix, Martin Aircraft Company, and Maxson. The Maxson M33 turret mount was preferred and—on the larger M3 half-track (T1E2)—was accepted for service in 1942 as the M13 Multiple Gun Motor Carriage. The mount was also used on the similar M5 half track as the M14 Multiple Gun Motor Carriage.

Experimentally, the Quadmount was also tested in 1942 on a M3 Light Tank in place of the tank's turret but the project was not proceeded with.

Even as production of the two MGMC vehicles was underway, there was work to increase the firepower. Re-working the M33 to take four machine guns gave the M45 mounting.

The M45 Quadmount was the principal weapon (along with the 37mm gun) of highly mobile anti-aircraft artillery battalions deployed in the European Theater during World War II. These battalions provided invaluable air defense to much larger units, particularly field artillery. The M45 Quadmount units served as a very strong deterrent to strafing runs by enemy warplanes as, in addition to their gross firepower, its quartet of Browning M2HB "heavy barrel" .50 caliber guns were capable of being "tuned" to converge upon a single point at distances which could be reset while in use. Multiple-gun mounts were developed for the M2 Browning because the M2's rate of fire (450–550 rounds per minute) for a single gun was too low for anti-aircraft use.

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