As with World War 1 decades before, World War 2 itself was a war of big guns and the United States committed much work to this field in an effort to produce mighty weapons to help destroy enemy defenses and concrete fortifications at range. The "8-inch Howitzer M1" was such a development and its development was begun shortly after World War 1 had come to a close. However, it languished in limbo for the years between the wars until finally standardized in 1940 - in time for active service in World War 2. Its designation was eventually changed to M115 during the 1950s and the weapon went on to see combat during the Korean War (1950-1953), the Vietnam War (1955-1975), and several other modern conflicts that rules the era. The weapon remains in limited, still serviceable, numbers with several world armies today (2014). Others have either been scrapped or saved as outdoor showpieces.
Origins of the M1/M115 take it back to the fighting of World War 1 when the United States committed to a war that it was not properly outfitted for. The Army lacked much in the manner of war-making goods and relied on the developments of others - such as those by Britain and France - to shore up its stocks. The Army eventually began use of the British 8" BL Mk VI howitzer which American factories were already committed to producing for the British. The weapon showcased good range and excellent accuracy and familiarity eventually proved key for further American evolution of the product.
With the war over through the November 1918 Armistice, the Americans retained their big gun stock and looked to further strengthen its qualities for the long haul. A committed was then arranged for the process and the group furthered both a 155mm (6") gun (to become the mighty M2 "Long Tom") and a 203mm (8") design. Both guns were to benefit from the use of the same split-trail carriage/two-wheeled limber transport system though the guns and their respective mountings would not be outright interchangeable without considerable work.
Despite the direction, the program languished until picked up again in the 1930s run-up to World War 2. By this time, the barrel had been lengthened for extended engagement ranges as well as better accuracy. Development work was restarted in 1939 which led to standardization the following year as the "8-inch Howitzer M1". The weapon was a complete artillery system fielding its powerful 203mm gun tube which was sat upon its elevation (-2 to +65 degrees) and traverse (+60 degrees) hardware. A hyropneumatic recoil system helped to counter the inherently violent recoil effects of firing such a large projectile as did four spades installed prior to firing. The breech was managed through an interrupted screw system and the carriage became a heavy-duty steel frame utilizing eight large road wheels under the mass of the gun. With the split-trails brought together, this tow arm allowed the vehicle to be hauled to the various battlefronts via mover vehicle. The typical operating crew was fourteen men and ammunition and charges were carried by support vehicles.
Each HE projectile weighed 200lb and were coupled to bagged propellant charges. There proved two HE models in play - the initial "Mk 1A1" shell (also used in American coastal defense guns) and the improved "M106" projectile. Both weighed the same but the latter held a range of 11 miles (versus 6.3 miles of the Mk 1A1) and a muzzle velocity of 1,950 feet per second (versus 1,340 fps). A "dummy" projectile was designated as "Dummy Mk 1". The crew could sustain fire at about three rounds for every two minutes but the standard rate was actually closer to a single round-per-minute.
The guns became largely available from January 1944 onwards and, in practice, these weapons shined in their given roles thanks to strong refinements of an already excellent British system. Accuracy was such that the guns could be used in the close-support role, laying indirect fire atop enemy positions quite close to "friendlies". Its massive 203mm shells were ideal in clearing out concentrations of enemy troops, defeating fortified positions, and even engaging light armor vehicles who happened to be in the path of the falling explosive. If the weapon could be towed to a given front, it held the capability of changing the fortunes of the attackers considerably - such was its value in-the-field.
Like other useful battlefield guns, the M1 was eventually mated to a variety of self-propelled, tracked vehicle chassis projects - some successful, others not. The T89 was a development that eventually became the adopted "M43 Howitzer Motor Carriage" (HMC) while the T80 and T84 were never adopted and served only in early pilot roles. One of the more famous adaptations of the gun tube was through the storied M110 SPH of Vietnam War fame - this vehicle saw considerable service throughout the remainder of the Cold War years.
Redesignated as the M115 during the 1950s, the weapon eventually joined the inventories of Croatia, Denmark, Italy, Iran, Iraq, Japan, Pakistan, Sudan, Taiwan, Turkey. Some - such as those with the Pakistani Army - remain in service today (2014). Modernized M115 gun forms were modified to fire NATO-standard munitions as well as nuclear shells.
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