M75
Introduction
M75 automatic grenade launcher
M75 automatic grenade launcher seen on an XM9 helicopter mount. Note the cam drum mounted on top of the square receiver.
Source: US Army -
© Public domain
Description
Introduction
The M75 is an early Cold War era automatic grenade launcher of US origin. The M75 was developed as an automatic grenade launcher for aircraft use. For this reason a higher velocity 40x53mm family of grenades was developed. The M75 was the first weapon to use these high velocity grenades, which remain in widespread service in many weapon systems today. The M75 was rather short-lived, being replaced by the M129.
Design
The M75 was the first automatic grenade launcher developed for helicopter use. The whole firing cycle of the weapon is electrically powered by a single electric motor. This is fed by an external power source. A cam assembly located in a drum actuates all moving parts and the feed cycle. Upon firing the barrel reciprocates. On the M75 the electric motor and cam drum are located on top of a box shaped receiver that houses the barrel and feed mechanism and firing mechanism. This setup has issues with torque during operation and in the improved M129 this was redesigned in having the barrel enveloped by the cam drum.
Firepower
The M75 fires the 40x53mm grenades at a cyclic rate of fire of 215 to 230 rpm. Maximum range is about 1.9 km. Upon introduction only the M384 high explosive grenade was fielded. This can be used against infantry and softskin vehicles. The fragmentation radius is about 15 meters. Ammunition supply depends on the mount. The M5 nose turret was connected to 150 or 302 round belts.
Platforms
The M75 was fielded on many helicopters in various types of mounts. The XM13 gun pod was intended for helicopters, but could also be fitted to A-1 Skyraider and OV-1 Mohawk but was hardly ever used on fixed wing aircraft. The M5 armament subsystem an a nose mount for the M75 on the UH-1 and ACH-47 Guns A Go-Go. The M28 chin turret for the AH-1 Cobra could mount the M75, often alongside a M134 six barrel minigun. The M75 was fitted for trials on a tripod normally used for the M2HB heavy machine gun. It was tested in this set-up, but not actually fielded in this way.
Users
The M75 was acquired by the US Army which used it on a variety of helicopters. It was actively used during the Vietnam war. The M75 was quickly replaced by the improved M129. The M75 seems to have been exported in small numbers to nations that acquired weapons from the USA in the 1970's as integral part of some helicopter types.
Details
Media
M75 automatic grenade launcher
Prototype XM75 seen in test setup on a tripod mount. Note the wire attached to an external power source. The M75 was never fielded on tripod for infantry use.
Source: US Army
Copyright: Public domain
M75 automatic grenade launcher
Right side view of M75 automatic grenade launcher.
Source: US DoD
Copyright: Public domain
M75 automatic grenade launcher in M28 turret
Close-up view of M28 turret on AH-1 Cobra attack helicopter. Note the M75 alongside the six barrel 7.62mm M134 minigun.
Source: US Army
Copyright: Public domain
M5 armament subsystem
Line diagram and photo insert of M5 armament subsystem with M75 automatic grenade launcher.
Source: US Army
Copyright: Public domain
M75 automatic grenade launcher
M75 automatic grenade launcher seen in an M5 helicopter chin turret. This was used on the UH-1 and ACH-47.
Source: US Army
Copyright: Public domain
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Mk 19 MOD 3
The Mk 19 automatic grenade launcher was developed as a crew served and vehicle mounted weapon using the same 40x53mm high velocity ammunition developed for the M75. The Mk 19 is better suited for ground use since it does not required external power since it is blowback operated.