A gun’s caliber refers to the diameter of its barrel, and a bullet’s caliber refers to its diameter
The cartridge is made up of four components, a metal bullet (projectile) that sits on top, the case which is usually made of nickel, brass or steel, and the primer that ignites the gunpowder.
The metal bullet’s weight is measured in grains. The weight affects the way it flies and how it performs when it hits a target. A heavier bullet travels slower but hits with more momentum, while a lighter bullet has a flatter trajectory and greater velocity.
The cartridge, commonly called “the bullet” comes in many sizes
The .22 is the most common caliber regarding units sold. The average weight of this bullet is roughly 20-40 grains. These bullets are only a few steps up from a pellet gun round. As a firefighter, I can tell you I went to a call one night in which a man was shot in the forehead with a .22, and the bullet lodged just under the skin but did not penetrate his skull. He was sitting up talking when we arrived. A hard head, distance, weak bullet, or a combination of them all, saved his life.
The .25 ACP is slightly larger than the .22 LR and slightly more powerful.
The .380 ACP, sometimes called a “9mm short” is a low power round that works best at close range.
The 9mm is used by the majority of police forces around the world. Its weight varies between 115-147 grains and has very low recoil. For most shooters, this is the go-to round.
The .40 S&W is stronger and more powerful than the 9MM, and a little bit heavier.
The 10mm has incredible stopping power with a harsh recoil.
The .45 ACP has a lot of power behind it. With around 230 grains and moderate recoil, it is a good self-defense choice.
The .38 special is most commonly found in revolvers. It has a longer cartridge and more powder, but it is slower than a 9mm.
The 7.62X39MM is a Soviet round designed to be used in the AK-47. Its average weight is roughly 123 grains.
The 5.56X45MM/.223 have almost identical dimensions. The .223 has a slightly lower pressure than the 5.56. It has long-range accuracy, which makes it a good option for people who might want to use it for self-defense.
The .308/7.62x51mm have almost identical dimensions as well. The .308 is the most preferred caliber for snipers all over the world.
The .30 Carbine was designed for the M1 Carbine and still popular with civilians.
The 5.7x28mm is a small bullet that travels very fast and allows for increased penetration with low recoil and high magazine capacity. It ranges from 23-31 grams.
The .357 Magnum has excellent stopping power and mainly designed for revolvers.
The .300 Blackout is designed to give the ballistic performance of a larger “.30 caliber” AK 7.62x39mm round but designed for the AR-15. It is popular because of its flexibility and power.
The 7.62x54mmR was designed by the Russians for their Mosin-Nagant. It is the oldest cartridge still in combat use.
The .30-06 Springfield has a strong recoil and good range. Its weight is around 150-180 grams.
Shotgun shells come in different gauges. The most common gauge in use in the U.S. is the 12 gauge, but 28, 20, 16, and 10 gauge are available. Shotgun ammunition varies depending on what you’re using it for. Birdshot is the most typically used shotgun ammo containing many smaller balls of metal. Buckshot is actually the same as birdshot but with metal balls that are bigger in diameter. And slugs are usually a piece of solid metal weighing 1 ounce.