Note that in some cases a three-number caliber size does not mean an extremely large caliber. For example, .223 simply means 22,3 caliber. Also, if measured in millimeters, the first number stand for width and the second for length.
- 5.56x45mm NATO. NATO intermediate round. Used by both NATO forces and countless others.
- .223 Remington. The civilian version which the 5.56x45mm NATO is based on.
- 7.62x51mm NATO. NATO full-power round. Not as popular as the 5.56x45mm NATO but still common with some non-NATO forces.
- 12.7x99mm NATO (.50 BMG). NATO heavy round. Commonly used in many anti-material rifles such as the Barrett M82, the McMillan Tac-50 and the Steyr HS .50.
- .308 Winchester. Very popular civilian cartridge which the 7.62x51mm NATO is based on.
- 7.62x39mm. Russian cartridge popular both amongst militaries and civilian shooters.
- 5.45x39mm. Newer Russian cartridge, used by the Russian military and many of their weapon-buyers.
- .22 Long Round. Lightweight .22 caliber ammo, both cheap and common amongst civilian shooters.
- 9x19mm parabellum. Common pistol round.
- .45 ACP. Another common pistol round, though not as common as the 9x19mm parabellum.
Many cartridges, especially military cartridges, are based on other cartridges and are similar enough to the cartridges they are derived from that you might consider interchanging them. In zombie-infested world, ammunition will be scarce and often you will need to use what you have. It depends mostly on the gun and the similarities of the cartridges to determine whether they are interchangable. Some guns might be more vulnerable to jamming or might simply not work if cartridge changing, and some guns might even explode. It has been shown that most NATO rounds can accept their civilian counterpart and vice-versa. Still, even if a weapon does accept the cartridge change, its performance may be affected (such as having poorer accuracy).