What Is the Main Difference Between Centerfire and Rimfire Ammo?
One of the most interesting things about ammunition is that there are such a wide variety of types in all kinds of shapes, sizes, and firing methods. There are so many choices, you might feel like you're at a buffet when shopping for ammo. When it comes to firing method, though, the two main categories of ammunition are rimfire and centerfire cartridges.
If you've ever wondered about the differences between the two, as well as the pros and cons for each, keep reading.
What Does Rimfire or Centerfire Mean?
The names rimfire and centerfire refer to two distinct methods of firing the bullet once the cartridge is struck. These two methods remain the only two ways in which a round is fired despite many variations on cartridge design over the years.
The names rimfire and centerfire are references to the placement of primer in the overall cartridge and how powder is ignited once it's struck. The difference between the two is just in how the cartridge is struck in order to fire the round. While it may sound simple, there's more to the story.
Understanding Rimfire Cartridges
The History of Rimfire Cartridges
The first rimfire cartridge was introduced in 1845 and was one of the first types of self-contained cartridges invented. It was a .22 caliber round called the .22 BB cap, or the 6mm Flobert after its French inventor Louis-Nicolas Flobert. The method remains viable and popular today. It's used in the current .22 long rifle round, which is the most common ammunition in the world today when it comes to the number of units sold.
Throughout the years, a number of different calibers were produced with this method, but the smaller calibers remain the most popular. The main calibers found in rimfire are variations of the .22 and the .17HMR. While larger caliber rounds can be found in rimfire production, they're few and far between. It simply isn't cost effective for many rounds because of production cost and lack of demand.
How Rimfire Cartridges Work
A rimfire cartridge fires when the striking method of the gun hits the rim at the bottom of the cartridge. In a rimfire cartridge, the primer (the element that ignites the main powder charge of the round) is contained in the endcap at the base of the round. This endcap is crushed by the strike that occurs when the trigger is pulled; that ignites the main powder, which propels the round down the barrel and out of the gun.
Advantages of Rimfire
Perhaps the biggest advantage to the rimfire cartridge is its availability. The .22LR is widely available and a very useful round for target shooting, small game hunting, and dealing with pests. Rimfire is also more secure against the elements and moisture because the primer is in the rim and there's no primer cup to insert. This creates a more sealed round.
Rimfire Drawbacks to Consider
However, there are some drawbacks to rimfire ammunition, the most notable being reliability. Because of the manufacturing process and the nature of the rounds, sometimes when the rim is struck, there isn't enough primer present to produce the explosion to ignite the powder. No one likes malfunctions of any kind, and while this is admittedly a rare occurrence, it happens enough to warrant awareness when choosing this kind of ammo.
Another drawback is that rimfire cartridges cannot be reloaded. The brass can’t be re-primed, making them unusable after being fired only once. This is certainly not an issue for everyone, but if you like to reload your ammo or were considering doing so in the future, it's definitely a detractor for this type of cartridge.
Understanding Centerfire Cartridges
You may have guessed by now that centerfire cartridges have the primer placed in the center of the cartridge. In centerfire rounds, the primer compound is placed in a small cup that sits in the bottom center, making it a two-piece construction. That's in contrast to rimfire cartridges, which are one solid piece.
When a gun is fired, the firing pin hits the center of the primer causing it to ignite. But in the case of centerfire cartridges, only the primer is destroyed. The rest of the process for launching the round down the barrel and out of the gun is the same as it is for rimfire.
Advantages of Centerfire
True centerfire cartridges were invented in 1829 by another Frenchman named Clement Pottet, although they weren't quite perfected. After much refinement, Pottet finally achieved the reliability and desired result in 1855. Over time, centerfire cartridges have undergone various revisions from numerous other individuals while remaining largely the same type of cartridge. Thanks to these design refinements, centerfire cartridges are more reliable and durable than rimfire options when it comes to being handled and fired in conditions that involve movement or jostling of the ammo. As a result, centerfire is a popular choice by the military.
Another positive to centerfire ammunition is that it can be reloaded. Since the primer is the only thing completely destroyed, the casing can be reused.
Centerfire Drawbacks to Consider
The main drawback to centerfire ammunition is that there are more places for moisture to enter the round, rendering it unusable. While this is unlikely in most situations, it's certainly worth being aware of so you can attend to proper ammo storage (How To Store Ammo).
Additionally, the more pieces that go into the construction of an item, the more points there are for failure. This isn't generally a concern if the ammo is properly made. However, it's important to be aware of this issue, especially if you're shooting cheaper ammunition or reloads.
Hopefully, you now have a better understanding of rimfire and centerfire cartridges and how they both work.