.22 Eargesplitten Loudenboomer is a cartridge

Cartridge (firearms)

A cartridge, also called a round, packages the bullet, gunpowder and primer into a single metallic case precisely made to fit the firing chamber of a firearm. The primer is a small charge of impact-sensitive chemical that may be located at the center of the case head or at its rim . Electrically...

 for a rifle

Rifle

A rifle is a firearm designed to be fired from the shoulder, with a barrel that has a helical groove or pattern of grooves cut into the barrel walls. The raised areas of the rifling are called "lands," which make contact with the projectile , imparting spin around an axis corresponding to the...

.

It was invented in the 1960s

1960s

The 1960s was the decade that started on January 1, 1960, and ended on December 31, 1969. It was the seventh decade of the 20th century.The 1960s term also refers to an era more often called The Sixties, denoting the complex of inter-related cultural and political trends across the globe...

 by P.O. Ackley to set a world record for firing bullets at over 5000 fps

Feet per second

The foot per second is a unit of both speed and velocity . It expresses the distance in feet traveled or displaced, divided by the time in seconds...

 (1524 m/s). The round failed to reach the desired velocity, but reached 4600 fps with a 50 grain bullet and 105 grains of H570 powder. It is based on the .378 Weatherby Magnum

.378 Weatherby Magnum

The .378 Weatherby Magnum was designed by Roy Weatherby in 1953. It was an original belted magnum design with no parent case, inspired by the .416 Rigby and headspacing of the belted .375 H&H Magnum. The 215 magnum rifle primer was developed by Federal specifically for this round. The cartridge can...

 cartridge case, necked down to .224 calibre.