self-propelled, howitzer motor carriage m7
M12 155mm Self propelled gun
Following World War I numerous designers approached the problem of motorizing artillery pieces to make them more mobile in the field. Although tanks had made their debut during the war, military planners also saw the need for a distinct type of self-propelled field artillery to accompany and support infantry. In 1919, the noted U. S. tank designer J. Walter Christie (1856-1944) mounted a 155mm gun on a special chassis equipped with tracks for cross-country use and wheels for road transportation. Although Christie’s designs found little favor at home (he later worked extensively for the British and the Soviets), he did set the groundwork for later developments.
As self-propelled gun and tank crews were required to operate in confined spaces, it also became necessary to find some method of reducing the choking fumes released at the breeches of their pieces after firing. To prevent such leakage, designers often incorporated fume extractors into their barrel designs. The fume extractor was a barrel-shaped compartment around the cannon tube somewhat past its midsection. As the fired shell passed the fume extractor, holes drilled through the barrel allowed a portion of the highly pressurized gas to enter its outer chamber. Once the projectile cleared the muzzle the pressure was then released, thus forcing the majority of the propulsive gasses toward the muzzle rather than the breech.
Although the proponents of the opposing schools altered their basic doctrines to suit the situation, during World War II two main schools of thought emerged concerning the proper use self-propelled artillery. The United States and Britain generally utilized their self-propelled guns in a conventional, indirect-fire infantry support role. In contrast, the Soviets and Germans tended to use theirs as rapidly advancing, infantry-accompanying direct-fire weapons.
Another early attempt at providing self-propelled field artillery equipment, the Priest consisted of a U. S. M2A1 field howitzer mounted on a M3 Grant tank chassis. Owing to the pulpit-like appearance of the Grant’s machine gun cupola, British crews quickly christened the weapon “Priest,” thus beginning their nation’s tradition of giving self-propelled field guns names with religious connotations. Also known as the 105mm Self-Propelled Howitzer M7 in U. S. service, some 3,500 Priests were manufactured and entered service between 1941 and 1943. The Priest saw action with British forces during the October 1942 Battle of El Alamein and was finally replaced in British service by the Sexton and in the United States by the M37 in 1945.
During the first months of World War II, the United States was forced to improvise to provide its forces with self-propelled artillery. In an early attempt to provide a self-propelled gun, in June 1940, U. S. engineers adapted the venerable 75mm M1897A gun to the M3 halftrack chassis. Adopted in 1941 and obsolete in 1944, the 75mm Gun Motor Carriage M3 had a mere 1,933-yard range, firing up to 15-pound projectiles. U. S. forces used the M3 in all theaters of the war, and, although sometimes used as a tank destroyer, it was more effective as a mobile infantry support weapon.
As the 75mm gun was found deficient against modern armor, in 1941 the higher-powered 105mm M1A2 howitzer was mounted on an M3 or M4 tank chassis to create the 105mm Howitzer Motor Carriage M7. The first M7s saw service with U. S. forces in the Philippines in 1941, and they proved particularly effective in British hands against Afrika Korps panzers at El Alamein in 1942. An adaptation of the French 155mm GPF gun to motorized use, the 155mm Gun Motor Carriage M12 was mounted on an M3 tank chassis. With a crew of six, it was adopted in 1941 and proved very effective in the European Theater during World War II. It was capable of a maximum range of 21,982 yards.
With a crew of four, the 75mm Howitzer Motor Carriage M8 mounted a 75mm M2/M3 howitzer on an M5 light tank chassis and was adopted in 1942. Secondary armament consisted of a caliber .50 machine gun mounted at the rear of its open-top turret. The M8 had a maximum range of 9,613 yards and saw extensive service during World War II, with a total of 1,778 being manufactured by the end of the war.
With a crew of seven, the 105mm Howitzer Motor Carriage M37 incorporated the 105mm M4 howitzer mounted on a modified M24 Chaffee light tank chassis. Adopted in September 1945, only 150 were accepted by the government. The M37 had a maximum range of 12,000 yards, and a caliber .50 machine gun was mounted in a cupola to the right of the howitzer as secondary armament.
Adopted in February 1945 and used in the Korean War, the 155mm Gun Motor Carriage M40 mounted either a 155mm Gun M1A1 or M2 mounted to the rear deck of a modified M4 medium tank chassis. Crewed by eight men, it had a range of 25,722 yards firing a 95-pound projectile. The 155mm Howitzer Motor Carriage M41 was adopted in June of 1945, and a total of 85 were accepted by the army. It incorporated a 155mm Howitzer M1 with a maximum range of 16,360 yards on the rear of an open M24 Chaffee light tank chassis. The M41 saw service in both World War II and the Korean War.
Adopted in June 1945 and with a limited production of only 48, the 8-inch Howitzer Motor Carriage M43 incorporated an 8-inch Howitzer M1 or M2 barrel that had a maximum range of 18,515 yards firing a 200-pound shell. Mounted to the rear deck of an M4 medium tank chassis and with a crew of eight, it was used extensively in the Korean War. Anticipating the need for heavy, self-propelled artillery for the invasion of Japan, the U. S. Army also adopted the 240mm Howitzer Motor Carriage T92 and 8-inch Gun Motor Carriage T93 in 1945. The heaviest U. S. self-propelled weapons of the war, both were mounted on a M26E3 Pershing heavy tank chassis and were manned by a crew of eight. The T92 used the 240mm Howitzer M1, whereas the T93 mounted the 8-inch Gun M1s. The T92 had maximum range of 25,262 yards firing a 360- pound shell. A large spade mounted to the rear of the chassis absorbed recoil, and a T31 cargo carrier provided ammunition. Owing to Japan’s surrender, only five T92s and two T93s were delivered.