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.
The M45 Quadmount was the principal weapon (along with the 40mm Bofors 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, the four .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) was too low for anti-aircraft use.
The M45 found use throughout the war as a land-based weapon, particularly during the Battle of the Bulge. Although the Allies achieved air supremacy by the invasion of Normandy in June 1944, German attack runs were still a threat. German fighter-bombers could approach and attack at low altitude and then quickly retreat to avoid Allied fighters. The Luftwaffe also mustered a large number of planes for the massive Operation Bodenplatte New Year's Day 1945 attack. At Oppenheim, when the Allies were gathering to make a massive push after crossing the River Rhine (March 1945), 248 German warplanes were used in an effort to destroy the bridge first. U.S. Army anti-aircraft artillery battalions massed, shot down 30% of the attacking force mainly with M45 Quadmounts and prevented the bridge from being touched before the U.S. Third Army went into Germany.
The M45 Quadmount was of little use against the new, fast-flying planes of the Jet Age; however it saw continued use against infantry targets in US post-war service.
The TCM-20 was a postwar Israeli development of the M45 mount, equipped with two 20mm Hispano-Suiza HS.404 cannons in lieu of machine guns. In frontline Israeli service, it was replaced by the M163 Vulcan Air Defense System in the 1970s, but some reserve units still used TCM-20s into the 1980s. The weapon was also exported to several third-world countries.
The M45 was combined with a variety of towed or self-propelled mounts; namely the M20 trailer, a light single axle trailer; or with the M17 trailer, a heavier tandem axle trailer based on a searchlight platform. When combined with the M17 trailer, they M45 system was called the M51 Multiple Machine Gun Carriage, and when combined with the M20 trailer it was called the M55 Machine Gun Trailer Mount.
It was also mounted on the M3 Halftrack for greater mobility, in which it was called the M16 Multiple Gun Motor Carriage.
The M45 is operated by two loaders and one gunner. The mount is capable of traversing a full 360 degrees around, with an angle elevation between -10 and +90 degrees. Traverse and elevation are electrically driven, powered by two rechargeable 6-volt batteries. All four guns could be fired at once, but standard practice was to alternate between firing the upper and lower pair of guns, allowing one pair to cool while the other was in use. This allowed for longer periods of action as overheating of the gun barrels was lessened.
The "tombstone" model M2 ammunition chests held 200 rounds apiece — with one ammunition chest on an M45 system holding ten times as many rounds as each of the quartet of twenty-round 20mm magazines of the German Flakvierling system held (and which, on the German ordnance system, had to be changed every six seconds on each gun of the quartet to ensure its own top 800 rpm "combined" firing rate), with each M2 ammo chest weighing 89 pounds apiece when full.
- Cortlandt V.R. Schuyler
- List of U.S. military vehicles by supply catalog designation
- Flakvierling 38, quadruple 20 mm autocannons mountable onto a Sd.Kfz. 7/1 half-track
- TM 9-2800 Military vehicles dated 1947
- TM 9-2010
- TM 9-1223
- FM 44-57
- SNL G220
- TM 9-789
- SNL G221
- TM 9-881