Caliber .30 ammunition
Rifle and carbine trials selected the Krag-Jorgenson as the standard U.S. Army rifle and established the .30-caliber (7.62 millimeter) which retained the standard for U.S. military rifles well into the 1960s. The .30-caliber rifle re-surfaced during the war on terrorism as units clamor for M14s or other .30-caliber rifles for issue to designated marksmen.
In 1890, a board convened which resulted in the selection of the Danish Krag-Jorgenson system as the first U.S.-issue repeating rifle utilizing smokeless powder. This took advantage of a technological breakthrough which had occurred in France. In 1886, French government chemist Paul-Marie-Eugène Vieille perfected the first smokeless powder practical for use in rifle caliber arms. The even .30-caliber was chosen as being the smallest admissible. Initially adopted as the Model 1892, the Krag remained the primary Army service rifle until the adoption of the Mauser-based Model 1903 Springfield. Copies of the .30 caliber semi-automatic gas actuated carbine, well-known as the basic military semi-automatic firearm used by the United States Armed Forces, have proven to be very popular for sports use. Among its many advantages are its simplicity of construction permitting easy disassembly for cleaning, inspection and repair of its various sub-assemblies including the gunstock, receiver, barrel, bolt, operating slide mechanism and trigger mechanism.
During the 1930s the .30 calibre Browning water-cooled machinegun was in use by the Field Artillery for anti-aircraft defense on the march and in bivouac or position. The basis of issue of machine guns to Field Artillery troops did not provide sufficient firepower for anti-aircraft defense. No satisfactory artillery carriage mount had been developed to provide for defense on the march. Development of machine gun mounts continued with every reason to believe that a satisfactory carriage mount will be devised. In the meantime, tests had been conducted with the Browning .30 calibre automatic rifle in an effort to obtain a more efficient available means for anti-aircraft defense for Field Artillery troops. The .50 calibre machine gun had been eliminated from consideration for anti-aircraft defense for Field Artillery due to the superiority of the .30 calibre machine gun in point of hits per elapsedperiod of time, up to ranges of 1,000 to 1,200 yards.
The .30-Caliber M1941 light machine gun fired the standard .30-O6 cartridge from a curved, single-row 20-round magazine, which fed horizontally into the left side of the weapon. Firing both fully and semi-automatically, it had a cyclic rate of 550-600 rounds per minute, although a single operator reasonably could fire only 150-180 rounds per minute. The fully assembled length of this light machine gun was 42 inches, but it could be broken down to a mere 23 inches and carried in a parachute pack. These recoil-operated machine guns were used by all three of the Marine parachute battalions fighting in the Solomon Islands and by a special U.S.-Canadian unit in Europe. The M1941 Johnson rifle fires 10 rounds of standard .30-caliber ammunition from an integral rotary magazine which could be loaded without opening the bolt. Unlike the gas-operated Ml Garand, it is also recoil-operated. Invented in 1936 (the year in which the U.S. Army adopted the Ml rifle), the Johnson rifle did not go into wartime production until 1940.
During the early 1960s, the U.S. militarywas looking for a rifle or carbine that couldbe used in fighting communist forcesarmed with AK-47s in the jungles of South-east Asia. The U.S. had the 7.62 mm M-14 rifle and the .30-caliber M-1 carbine in its inventory, but no matter what modifications were made to either weapon, neither met the demands of the environment. What was needed was a carbine or a short-barreled rifle that would fire an intermediate-weight cartridge and was capable of full automatic fire.The M-14 performed well, but it was considered to be too heavy for soldiers to carry in the humid jungles of Southeast Asia. Because of the size and weight of the M-14's cartridge, soldiers could not carry more than 100 rounds on patrols, which severely limited the rifle's capability as an assault weapon. The M-1 carbine was lighter in weight than the M-14 and used a smaller cartridge, but the carbine's cartridge was considered to be severely under-powered. The U.S. eventually chose the 5.56 mm AR-15 rifle, the forerunner of the M-16, not because it was a superior weapon, but because it had greater capability for modifi-cation - it was capable of adapting.
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