Atlantic Firearms: Your Choice For Ammunition
Our Guide To Centerfire Vs. Rimfire Ammunition
Anybody who is familiar with firearms will be able to tell you: there are tons of different types of ammunition. If you go into most local gun shops or sporting goods stores you will find a massive variety of ammo for sale in various calibers, which range from small bore plinking rounds up to massive .50-caliber long-range ammunition, and tons of shotguns, rifles, pistols and much more.
Despite the practically endless variety of rounds that are available, almost all of them fall into one of the two major types of ammunition: centerfire or rimfire. Those two types of ammunition are named based on how their primer ignition system operates.
Every round of ammunition, whether it is centerfire or rimfire, is called a cartridge. There are four parts on every common cartridge - the projectile or bullet, some type of propellant, primer, and case. Sometimes the word "bullet" is used mistakenly instead of "cartridge," however that refers to just the projectile, instead of the entire assembly.
Whenever a gun is fired the cartridge's primer is impacted by the firing pin, which creates a small explosion to ignite the propellant, within the case. The bullet is propelled by the ignition out of the case and then down into the barrel, which heads towards the target. The way that the primer system works is the difference between centerfire and rimfire ammunition.
As previously mentioned, rimfire ammunition gets its name from the priming compound that is spun inside of the case's rim. Whenever the cartridge's rim is struck by the firing pin, the primer is ignited. Typically rimfire cartridges are usually limited to only the lower pressure, which leads to fairly small calibers, such as the regular .22 Long Rifle (LR).
Rimfire ammunition dates all the way back to 1845 when the very first rimfire metallic cartridge was conceived by Louis Nicolas Auguste Flobert, who was a French inventor. Coming out of the 1831 patent, the cartridge from Flobert featured just a percussion cap that a bullet attached to it, with no powder. The cartridges produced low velocities and were designed for use within indoor shooting galleries.
The .22 Short, was designed for the Model 1 Smith & Wesson revolver and came out in 1857. It used black powder for propelling a conical projectile. That started an evolution among rimfire cartridges that resulted in .22 LR and became one of the all-time popular cartridges.
Although the .22 LR is currently the rimfire caliber king (with competition from the Hornady Magnum Rimfire .17 HMR), with the earliest rimfire rounds that include larger calibers, including .44, .41, .38, .32 and .30, along with the large .58 Miller. When the smokeless powder was introduced it resulted in larger calibers being abandoned, since much higher pressures are generated by smokeless powder compared to black powder. That resulted in needing to use less propellant, and that demanded rounds that were scaled-down. Ammunition and firearm makers found that centerfire ammunition was a much better option for the bigger projectiles that the smokeless powder propels.
The primer in the centerfire cartridges is hosted in the middle of the head of the cartridge case, which is where the name comes from. Most ammunition that is produced these days is centerfire, with just small calibers produced with rimfire, which includes shotgun, rifle, and pistol ammunition.
The primer within the centerfire rounds is inside a metal cup holding a primary explosive. The gun's firing pin impacts the primers and the explosive is crushed between an anvil and cup, which produces incandescent particles and gas that ignites the smokeless powder. For centerfire ammunition, there are two types of primers that are available: Boxer and Berdan, which are both named for their inventors (with both being colonels interestingly enough).
Berdan primers, which were invented by Colonel Hiram Berdan from New Ork. The first version of the primer was patented in 1866. It was built initially for using copper shells, but problems with reliability were revealed by testing, specifically that the swelling of its shell prevented the cartridge from being seated in the chamber. The design was improved by Berdan by changing to brass cases and adjusted the installment of the primer cap, which created a design that is still the same today.
Colonel Edward Boxer from the Royal Arsenal located in Woolwich, England, created Boxer primers, got a patent in England in 1866 and in 1869 a U.S. patent for his primer. It was very much like the Berdan primer, but the main difference is where the anvil is located. The boxer primer's separate stirrup design doesn't make any difference in performance but does allow for the spent primers to be easily removed. That makes it easier to reload the case also.
This has resulted in all commercial centerfire ammo that is U.S. factory made is Boxer primed, with a high amount of imported European ammunition is Berdan primed, that is time-consuming, expensive and difficult to reload.
There are Boxer primers available in different sizes - for the small rifle, small pistol rounds a 0.175-inch is used, for inline muzzleloaders and shotgun shells a 0.209-inch is used, and for large pistol and rifle rounds a 0.210-inch is used, while for .50 BMG and other similar ammunition 0.315-inch is used.
When choosing ammunition, especially when it comes to your cleaning regimen for firearms, many military surplus ammunition uses corrosive Berdan primer (but most Boxer primers, by contrast, are non-corrosive.) rrlThose Berdan primers have a tendency to be more reliable in an austere environment, but they can be difficult for firing pins to accurately strike, and leave corrosive materials inside of the barrel and the firearm's action after firing.
Whenever military surplus or ammunition is used with corrosive primers, make sure to clean your firearm thoroughly after using it in order to avoid damage and pitting to internal components, and think about having an enhanced firing pin installed that can impact the primer properly to ensure the proper ignition.