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Wednesday, September 29, 2021


The .22 Eargesplitten Loudenboomer cartridge was developed by P. O. Ackley for Guns & Ammo magazine. Its sole goal was to produce a muzzle velocity of at least 5000 feet per second (fps) or around 1524 metres/second, in excess of Mach 4.2. The cartridge was created by necking down a .378 Weatherby Magnum case to accept a 3 gram .224" (5.56 mm) bullet.

In ballistic testing, the round never achieved the target muzzle velocity, topping out at 4600 fps (1500 m/sec) and a muzzle energy of 3,185 joules, which is almost twice that of the 5.56×45 NATO cartridge used by the AR-15, M-4, and similar rifles, which fires a bullet of comparable size and mass.

It is not clear what would have happened to the bullet immediately after leaving the barrel. At Mach 4, heating and aerodynamic forces would have been extreme, and it's possible a lead bullet might have melted shortly after exiting the muzzle and been dispersed into a cloud of droplets. In any case, with such a light bullet and supersonic drag forces,, the projectile would rapidly lose velocity and energy. But this was intended to set a record, not be practical for anything.

Posted at September 29, 2021 15:23