105mm Howitzer M3
The 105 mm Howitzer M3 was a light howitzer fielded by the US Army during WWII, and designed to provide heavier firepower than the 75mm M1 Pack Howitzer for use by airborne and mountain troops. The gun utilized a barrel derived from 105mm Howitzer M2 fitted to a modified split trail carriage from the 75mm howitzer.
Development and production
As the US Army began to construct an Airborne Division in 1941, a requirement surfaced for an air portable 105mm howitzer to provide better support than the lighter 75mm M1 pack Howitzer. The weapon that emerged to meet this demand consisted of a 105mm M2 barrel shortened by some 27 inches and mated to the 75mm M1 recoil system and 75mm M3 carriage. This 105mm Howitzer T7 was submitted for prototype trials at Aberdeen Proving Ground in March of 1942.
Intended to fire the same ammunition as the longer M2, trials showed incomplete combustion with standard propelling charges in the short barrel. This required a new series of charges of faster burning propellant which in turn called for a series of proof, calibration and ballistic trials that causes some delay. Otherwise the T7 was found acceptable and standardized as 105mm Howitzer M3 on Carriage M3. The Carriage was soon strengthened to M3A1 pattern, and over the next few years further strengthening was appalled to meet problems as they emerged with service, resulting in the M3A3.
The howitzer was designed to fire the same ammunition as the longer M2. It however, it turned out that shorter barrel resulted in incomplete burning of the propelling charge. The problem could only be solved by use of faster burning powder, but this demanded an extensive program of proof, calibration and ballistic trials which delayed its introduction to service. Otherwise the design was considered acceptable and was standardized as 105mm Howitzer M3 on Carriage M3. The carriage was soon succeeded by M3A1, which had trails made from thicker plate. Even stronger tubular trails were designed, but never reached production.
Production of the M3 started in February 1943 and continued until July 1944; with additional batches built during 1945 and 1946 for a total of 3,474 guns.
Although the M3 was originally intended for glider battalions, it came to see far wider service across the US Army. The first recipients and eventually the largest users of the M3 were the Cannon Companies formed in each Infantry Regiment during the latter half of 1943. M3’s were also substituted for a portion of the 75mm howitzers assigned to Mountain troops, and a number were provided to the Russian Army issue to their ski, mountain and partisan formations. Lastly some twenty pieces were distributed around Latin American countries as part of the US Military Aid program.
The M3 did not last long in US Service after the end of the war, and soon cropped up in re-emerging armies of Eastern Europe donated under the Marshall Plan, likewise many came from Russian sources as they were replaced by artillery pieces in standard Russian calibers. Many nations acquired small numbers of M3’s for use in arduous terrain, but as the piece was not demountable its utility as a Pack Howitzer was limited, and by 1960 the M3 had largely disappeared from front line service.
The M3 Howitzer used the same range of projectiles and 105mm Cartridge Case M14 as the 105mm Howitzer M2 with a unique set of faster burning charges in four increments over a fifth base charge. These elements were assembled as semi-fixed rounds; which is to say the case with charge, and shell were provided as two separate components, and assembled in the field before being loaded. This allowed the propelling charge to be adjusted by removing charge increments to change the ballistic trajectory while retaining the ease of handing a fixed round when feeding the gun. In an emergency standard M2 ammunition could be used but only up to Charge 3 and the M2’s Blank (Cartridge Case M15 with black powder charge) was standard for the M3 as well, a useful point as post war many M3’s ended up as saluting guns around various US Military installations.
• T7, standardized as M3.
• T10 - variant with elevation improved to 65 degrees.
• M3 - based on M3A1 carriage for the 75 mm field howitzer.
• M3A1 - had stronger trails, made from 1/8 inch plate instead of 3/32 inch.
• M3A2 - was fitted with shield.
• 105 mm Howitzer Motor Carriage T38 – proposed SPG on the M3 halftrack not pursued
• 105 mm Howitzer Motor Carriage T82 (M3 in mount M3A1) – SPG on M5A1 Light Tank chassis. Two pilots built, project canceled in July 1945 for lack of requirement