Vocabulary—Just What is the Difference Between Rimfire and Centerfire Ammunition?

Rimfire Cartridges

Rimfire cartridges contain their “priming compound” in the “rim” of the cartridge. The priming compound is what sparks to ignite the gunpowder within the cartridge case, while the rim is precisely where the firing pin strikes when the user pulls the trigger. The powder charge sits directly in front of the priming compound, so ignition is very reliable.

The beauty of the rimfire cartridges is in their simplicity. They are easily constructed, use a relatively small amount of powder, and generally generate low pressures. Those low pressures mean there’s not a lot of felt recoil for the user. Rimfire ammunition also produces less noise than most centerfire ammunition.

In the course of your research when looking to buy a rifle or pistol, odds are you’ve come across the terms “rimfire” and “centerfire,” used to define the type of ammunition a particular firearm uses. While more experienced shooters may toss these terms around loosely and with confidence, the terms warrant a bit of explanation for those new to the shooting sports. Ammunition for the modern rifles and pistols we use fall into one of those two categories, and it’s important to understand the differences between them.

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Centerfire Cartridges

Today’s centerfire cartridges are as different from their rimfire cousins as you could imagine. For one, hey use a much thicker brass case. More importantly, they use a component called a “primer.” If you’ve looked at the bottom of a .45 ACP, .38 Special or .308 cartridge, you’ll see a button-like fixture imbedded in the center of the brass rim. That button is the “primer.” It is an individual component that, during the manufacturing process, is fitted into the brass case. Like the full rim of a rimfire round, the primer is what contains the priming compound. When struck by the firing pin when the user pulls the trigger to fire the gun, that priming compound in that primer is crushed against a part of the primer that’s called an “anvil.” That crushing sends a shower of sparks into the powder charge within the case.

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Generally speaking, centerfire cartridges operate at significantly higher pressures than do rimfire cartridges. That also means more recoil and a louder bang, but the benefits are that centerfire rounds generate considerably higher velocities than their rimfire counterparts, important when shooting at longer distances and for hunting.

There are fantastic firearms chambered for both types of cartridges. Rimfire cartridges make a wonderful choice for target practice, plinking, and small game hunting, while centerfire cartridges perform those functions and can also handle large game, long-range shooting duties and self-defense roles.

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