ArmaLite Inc AR-10A4 243 Winchester 20" Barrel Black Fixed Stock Round Mag Semi-Auto 10A4243BF

Introduced in 1955, the 243 Winchester is based on the 308 Winchester case necked down. It was the first commercial cartridge added to the "308 family," with a 2.045-inch case designed to fit into Winchester's Model 88 lever action and short bolt actions. Winchester saw it as a combination "varmint and big-game" round, with an 80-grain varmint bullet at 3550 feet per second and a 100-grain deer bullet at 2960. Apparently the public saw it the same way; the 243 Winchester is the world's most popular 6mm cartridge, with current loadings running from a 55-grain varmint load at nearly 4000 fps to 108 grains. 6mm bullets hold up better in wind than smaller calibers, so the 243 remains a favorite for long-range varminting. With heavier bullets it is very effective on deer-sized game. Its attributes are accuracy, light recoil, and deadly effect; it is a standard choice for beginning hunters. Because of its popularity factory loads are legion, and most rifle manufacturers offer it. — Craig Boddington