Sunday, July 31, 2005

A Brief History of .50 BMG Cartridge Development @ AmmoGuide

AmmoGuide has A Brief History of .50 Browning Machine Gun Cartridge Development:
Tradition has it that the cartridge that was to become the .50 BMG we know today, was initiated at the personal request of General John (Blackjack) Pershing. This request for a heavy machine gun cartridge came in light of American experiences with the large-caliber weapons employed by the European nations during WW1. The request, in April 1918, for a weapon with an effective range of 6,000 meters and a muzzle velocity of 2600 fps was contracted to the Winchester Repeating Arms Company. The proposed cartridge was to have both machine gun and anti-tank capabilities.

Later that same month, Winchester began the fabrication of test cartridges to obtain ballistic data. Initially they used 16-gauge, brass shotshells, necked down to accept commercial 500-grain lead 45-70 projectiles. Propellant charges used varied from 120-150 grains, developing 2485 to 2944 fps muzzle velocity, and generated a (probably wildly overestimated) breech pressure of 90,000 psi!! (Compare that to the pressures developed in the current cartridges on the chart above.)

In late 1918, work on the cartridge was transferred from Winchester to Frankford Arsenal, where it remained (almost exclusively) until well into WW2. Design work on the weapon itself was performed by John Browning and Colt.

During the ensuing years of development, the cartridge case design went through a series of metamorphoses. Case lengths from 4.08 inches to 3.80 inches were tried. Rimmed, semi-rimmed, and rimless case designs were considered. Both the 13mm German anti-tank round and a scaled-up 30-06 cartridge design were copied, with the latter finally winning approval. Projectile weights from 800 to 508 grains were tested. And cartridge overall lengths from 5.51 to 5.00 inches were explored. (Compare with the stats listed in the chart above.)

Eventually, advances in tank armor outpaced that of anti-tank rifles, so the .50 BMG became, exclusively, a heavy machine gun caliber cartridge. The first machine gun was standardized as the M1921 and, in 1924, the Caliber .50 Browning Machine Gun Cartridge was adopted in the form pretty much as we know it still today.

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