A shelf of rifle ammunition looks like a list of random numbers, but most of it is two families and a few outsiders. One family runs from the .222 Remington to the .223 and 5.56 rounds that feed AR-15s. The other is the .30-caliber .308 Winchester and its relatives. Knowing which family a box belongs to tells you what it was built to do.

The small-bore family: .222, .223 and 5.56

The oldest member is the .222 Remington, introduced in 1950 and a benchrest favorite for decades. Anyone shopping for 222 ammo is almost always feeding a bolt-action varmint rifle, usually with a 50-grain bullet.

The .223 Remington followed in 1964 alongside the AR-15 and descends from the .222 Remington Magnum. Fiocchi, an Italian maker whose history goes back to the 1870s, loads it for sporting use, and fiocchi 223 ammo is where its .223 loads are gathered.

The military sibling is the 5.56x45mm. The 55-grain full-metal-jacket round the United States adopted for the M16 in the 1960s is the pattern behind m193 55 grain ammo. NATO standardized the 5.56 in 1980 around a heavier 62-grain bullet with a steel-core penetrator and a green-painted tip, the round collected under m855 green tip 5.56x45 fmj ammo.

If you would rather browse the cartridge as a whole, 5.56 ammo for sale brings the family onto one page.

The .308 family and its relatives

The .308 Winchester went on sale in 1952 and became NATO's 7.62x51mm in 1954, so nearly every maker loads it. Hornady, founded in Nebraska in 1949, is best known for bullets such as the SST and ELD-X, and its .308 loads are gathered under hornady 308 ammunition. Federal's match-grade lines use hollow-point boat-tail bullets, the kind of round behind federal 308 hollow point ammo.

The .260 Remington is the .308 case necked down to 6.5 millimeters. Remington standardized it in 1997, and it lost ground once the 6.5 Creedmoor appeared in the late 2000s, but owners of .260 rifles still go looking for 260 remington ammo for sale.

Two outsiders

The .405 Winchester dates to 1904 and the Model 1895 lever-action rifle, and Theodore Roosevelt carried one in Africa in 1909. It has been loaded with heavy bullets, typically 300 grains, and soft-point loads such as those at 405 winchester soft point ammo are the traditional choice.

From the other side of the Iron Curtain comes the 5.45x39, adopted in 1974 for the AK-74. Its bullet measures .221 inch against the 5.56's .224, so the two cartridges are not interchangeable even though they look alike. Imported boxes usually spell it with the millimeter mark, as in 5.45x39mm ammo.

Cartridge names are not interchangeable. Match the marking stamped on your barrel before ordering, and confirm current stock and any state shipping restrictions before checkout.