.222 Remington (REM)
The .222 Remington or 5.7×43mm (C.I.P), also known as the triple deuce, triple two, and treble two, is a centerfire rifle cartridge. Introduced in 1950, it was the first commercial rimless .22 (5.56 mm) cartridge made in the United States. As such, it was an entirely new design, without a parent case.[2] The .222 Remington was a popular target cartridge from its introduction until the mid-1970s and still enjoys a reputation for accuracy. It remains a popular vermin or "varmint" cartridge at short and medium ranges with preferred bullet weights of 40–55 grains and muzzle velocities from 3,000 to 3,500 ft/s (915–1,067 m/s).
