M116 howitzer

75mm Pack Howitzer M1A1 on Carriage (airborne) M8
Two M116 Howitzers, Chengkungling History Museum, Taiwan (2011)
Type	Pack howitzer
Place of origin	United States
Service history
In service	1927–present
Used by	United States, United Kingdom, France, the Philippines, Republic of China, Turkey, People's Republic of China, Viet Minh, Pakistan Yugoslavia
Wars	World War II, Second Sino-Japanese War, Korean War, Chinese Civil War, First Indochina War, Vietnam War, Kurdish–Turkish conflict
Production history
Produced	1927–1944
Number built	8,400
Specifications
Weight	653 kg (1,439 lbs)
Length	3.68 m (12 ft 1 in)
Barrel length	Bore: 1.19 m (3 ft 11 in) L/15.9 Overall 1.38 m (4 ft 6 in) L/18.4
Width	1.22 m (4 ft)
Height	94 cm (3 ft 1 in)
Crew	6 or more
Caliber	75x272mm (2.95 in)
Breech	Horizontal block
Recoil	Hydropneumatic, constant
Carriage	Box trail, dismantling
Elevation	+5° to +45°
Traverse	6°
Rate of fire	3–6 rounds per minute (sustained)
Muzzle velocity	381 m/s (1,250 ft/s)
Effective firing range	9,600 yards (8,778 meters)

The 75mm Pack Howitzer M1 (redesignated the M116 in 1962) was an artillery piece used by the United States. It was designed in the 1920s to meet a need for a howitzer that could be moved across difficult terrain. The gun and carriage was designed so that it could be broken down into several pieces to be carried by pack animals. The gun saw combat in World War II with the United States Army (primarily used by airborne units), with US Marine Corps, and was also supplied to foreign forces.

In addition to the pack / air portable configuration, the gun was mounted on a conventional carriage to serve as a field artillery piece. The M2 and M3 are derived vehicle mounted howitzers used in the 75mm HMC M8 and some LVT models. In addition, the M1 in its original version was mated to a number of other self-propelled carriages, though only one of those – 75mm HMC T30 – reached mass production.

The 75 mm pack howitzer was designed in the United States in the 1920s to meet a need for an artillery piece that could be moved across difficult terrain. In August 1927, the weapon was standardized as Howitzer, Pack, 75mm M1 on Carriage M1. Due to meager funding, production rates were low; by 1940, only 91 pieces were manufactured. It was not until September 1940 that the howitzer was put into mass production. By then, the M1 had been succeeded by the slightly modified M1A1. Production continued until December 1944.

The only significant changes during the mass production period were carriage improvements. The original carriage M1 was of box trail type, with wooden wheels. The requirement for a lightweight howitzer for airborne troops led to the introduction of the M8 carriage, similar except for new wheels with pneumatic tires. Another requirement, from the cavalry branch of the US Army, resulted in a completely different family of "field howitzer" split trail carriages M3A1 / M3A2 / M3A3. However, only limited numbers of the M1 field howitzer variant were built, due to cavalry's switch to self-propelled guns.

The howitzer M1 or M1A1 consisted of tube and breech, which were joined together by interrupted threads, allowing for quick assembly and disassembly. One eighth of a turn was required to connect or disconnect tube and breech. The tube had uniform, right hand rifling with one turn in 20 calibers. The breech was of horizontal sliding block type, with continuous-pull firing mechanism.