Ammo Basics: Centerfire and Rimfire

Although there are hundreds of different types of ammunition cartridges available, all ammunition can be divided into one of two categories. This blog entry will briefly discuss the differences in centerfire and rimfire ammunition cartridges.

Although there are many different kinds and calibers available, they can all be broken down into one of two main categories. Centerfire or Rimfire. There is a massive difference between the two. The first kind of ammunition I am going to talk about is the rimfire cartridge. The sample rimfire cartridge pictured below is a .22 Remington.


The rimfire is designed to have the all priming compound inside the bottom curved base of the cartridge. The firing pin of the weapon that uses this ammunition has to strike the entire bottom of the cartridge to discharge the bullet. Once the base is struck with sufficient force, all the priming at the base of the cartridge will detonate, causing the main powder inside the cartridge to ignite, and then the cartridge will discharge the bullet. All this happens in a few nanoseconds.


The second kind of ammunition cartridge is the centerfire cartridge. Centerfire cartridges are different from rimfire cartridges because of where the priming compound is located. Looking at the photo below, you can see there is an inner circle on the base of these cartridges. This inner circle contains the primer for the centerfire cartridge.


The firearm that uses the centerfire kind of cartridge only needs to strike the center of the base, and not impact the entire bottom of the cartridge. Usually, this is accomplished with a small pin-like protrusion at the end of the hammer of the firearm. Once the center is struck with sufficient force by a pin-like hammer, the primer will detonate, causing the main powder inside the cartridge to ignite, thereby discharging the bullet.


In the following photo you can see a shotgun shell has the same centerfire design as the previous handgun cartridges had. As a matter of fact, it functions on the exact same concept as the previous cartridges.


So why the design difference? Centerfire cartridges, by the way of their design, are much stronger, and can accommodate more internal pressure all around. More powerful internal resistance mean higher possible pressure and velocities can be put on these kinds of cartridges. As a result, bigger bullets can be discharged with a centerfire design than what is possible with a rimfire design. Virtually all modern firearms use centerfire cartridges. Only the .22 caliber ammunition series retains the rimfire design.


Another big difference in the design is their re-usability. When rimfire cartridges are discharged, the hammer of the firearm usually damages the base of the cartridge, and the primer is completely obliterated. This makes most rimfire cartridges useless after their initial discharge. However centerfire cartridges can be re-used by simply replacing the dented center primer, reloading the cartridge with gunpowder, and capping the top with a bullet. There are specific machines that are sold just for this purpose.


Re-loading centerfire ammunition is economical, as you can purchase gunpowder and bullets separately. Re-loading centerfire ammunition also allows for custom-tuned and designed ammunition as the individual sees fit. Have you ever noticed there are always nicely collected buckets of empty cartridges at the target range?


Its because someone who works there is keeping all of them to reload later! Reloaded centerfire ammunition used to be a better deal than buying from the stores, but with certain department stores purchasing ammunition by the warehouse full and offering them at steep discounts, this is no longer the case.

-end-