Rimfire ammunition and centerfire (archaically called “central fire” by some manufacturers) are different types of cartridge designs with different pros and cons. Since these terms are important to understand for new and experienced firearms owners, let’s go over the differences, as well as the advantages and disadvantages of both types and popular calibers.
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What is rimfire, or what does rimfire mean?
Rimfire refers to a firearm cartridge that has its priming compound located in a “rim” around the base of the cartridge casing. This is a very old design dating back to 1845 but remains popular to this day.
In a rimfire cartridge, wet, impact-sensitive priming compound is dropped into the bottom of a fully-formed brass (most commonly) case, and the case is then spun by machines to centrifugally move the priming compound outward into the internal space around the rim of the case. The case is then dried, charged with powder, and a bullet is seated and crimped in place to complete the assembly of the cartridge.
When the cartridge is inserted into the chamber of a suitable firearm and the shooter pulls the trigger, the firing pin, striker, or hammer hits the rim of the cartridge, indenting it quickly and deeply enough to set off the priming compound, which ignites the gunpowder and the resulting expanding gases drive the projectile down the barrel and out of the firearm.
The most common rimfire cartridge (by far) is the .22 Long Rifle or .22 LR, which we’ll cover in more detail below.
What is centerfire, or what does centerfire mean?
Centerfire cartridges utilize a more modern and reliable way of placing priming compound into a cartridge case. Rather than have the priming compound placed directly into the interior base of the case as with the rimfire system, a centerfire cartridge has an external “pocket” in its base, into which a separate, metal, cup-shaped “primer” is inserted, which contains the priming compound and, in the most common American-style “boxer” priming system, an “anvil” that assists the impact of the firing pin in compressing and igniting the priming compound for reliable ignition.
Note: for more detailed definitions of each component of a cartridge, see our complete gun owner’s glossary.
The most common centerfire cartridges in America include popular defensive handgun calibers like 9mm Parabellum, .38 Special, .357 Magnum, and .45 ACP, as well as rifle cartridges like 5.56x45 NATO/.223 Remington (a widely popular chambering for AR-15s), .30-30 Winchester, .30-06 Springfield, and 7.62x51/.308 Winchester.
What are the main differences and advantages between rimfire and centerfire?
There are important differences between centerfire and rimfire cartridges, along with the pros and cons of each. Let’s go over some of the main ones.
Fired rimfire (left) and centerfire cartridges. A rimfire firing pin produces a notch at the edge of the case; a centerfire pin produces a depression in the center of the primer.
Cartridge case design and primer location
As we discussed above, the primary difference between rimfire and centerfire cartridges is the location of the priming compound, and the respective cartridge names reflect this. Centerfire rounds use a separate, removable primer inserted into the external center of the cartridge base, while rimfire rounds don’t utilize a separate primer, but instead have their priming compound located internally, in the rim of the cartridge base. Firearms designed to shoot rimfire rounds necessarily have their hammers, strikers, or firing pins located to strike the outside edge of the firing chamber (where the rim of the cartridge is located), while centerfire firearms will have their hammers, strikers, or firing pins centrally located in order to strike the center of the chambered cartridge where the primer is located.
Thickness of the brass and resulting power
Since a rimfire cartridge’s brass case itself must be deformed relatively easily by the impact of the firing mechanism in order to function properly, the brass itself must necessarily be quite thin. This, combined with the stamped/sheet method for forming the thin brass case, means that rimfire cartridges can’t support the higher pressures and energy levels of centerfire cartridges, which can have very thick, supported “webs,” bases, and rims, and thicker case walls to help contain high pressures safely. Generally speaking, centerfire cartridges have much more power than rimfire cartridges. In many locations, hunting medium-sized or large game with rimfire firearms is prohibited, due to their lack of ethical killing power.
Bulk .22 rimfire ammunition is almost always the cheapest type of ammunition you can find. In non-panic-buying times, buying a single primer for centerfire ammunition might cost the same or even a little more than a complete .22 rimfire cartridge. This means you can shoot more, hunt more, plink more, and have lots of fun for relatively little cost when shooting popular rimfire cartridges. Premium match-grade rimfire ammunition can cost up to 50 cents per shot or more, but compared to premium match-grade centerfire cartridges, this is still a bargain. Match ammo for popular centerfire cartridges starts at around $1.00-$2.00 a shot, and some more exclusive rifle ammunition (say, for very powerful Safari cartridges) can be $10, $20, or even up to $100 per shot.
Recoil and muzzle blast
Modern rimfire ammunition projectiles are typically between .172” and .228” in diameter, with bullet weights between 17 and 50 grains. Powder charges are very small as well, compared to popular centerfire cartridges. This means that recoil is much, much less when shooting common rimfire cartridges compared to most centerfire cartridges. New shooters, recoil-averse shooters, older shooters, or anyone who just wants to shoot a lot without being bothered by recoil will appreciate shooting rimfire compared to centerfire.
While some rimfire firearms are still very loud (.22 Magnum handguns in particular), the concussive muzzle blast produced by the large volume of expanding gas in many centerfire guns is not present when shooting rimfire. If you’re shooting indoors or near other shooters, this can be a big factor.
Because of the way the priming compound is dropped into the rimfire case and then spun into the rim, there is a greater chance for voids or gaps in the primer area compared to a separate centerfire priming system. Using “bulk” .22 rimfire ammunition, misfire or “dud” rates of 8-10% are not uncommon with some types of ammo in some firearms. It’s just something you have to accept. Better brands of ammo and firearms can get that failure rate down to 1-2% or better. If you pay higher prices for premium rimfire ammunition or “match” ammo, you are generally paying for more labor in inspecting, manufacturing and quality-checking the ammo. This can result in a lower misfire rate, but it doesn’t entirely eliminate it. Generally speaking, the centerfire priming system is more reliable than the rimfire.
In addition to a more reliable ignition, the nature of the soft, coated/waxed/plated lead bullets used in most rimfire ammo, and the full-bore-diameter construction of some rimfire bullets, contributes to more potential bullet damage upon chambering, which can reduce accuracy and feeding reliability.
Additionally, the very small, light bullets fired by rimfire firearms may be very effective on small game and pests, but they don’t perform particularly well against human-sized threats in actual shootings. Generally speaking, if your life is on the line, it’s a better bet to go with quality centerfire ammunition rather than rimfire.
Rimfire cases are permanently deformed by the impact of the firing pin, striker, or hammer hitting the rim. This means that 99.999% of the time, rimfire cartridges can’t be reloaded. (There are some specialized tools and compounds that allow you to reload rimfire ammo in a true emergency, but it is so time-consuming and costly that it’s really not worth it, and almost nobody tries it.) A fired centerfire cartridge case, on the other hand, is usually fully reusable/reloadable, and the old primer can be punched out with a tool and a new one pressed in. Many people have reloaded their centerfire cartridge cases dozens of times.
Types of rimfire cartridges (popular calibers)
Now that we’ve gone over the main differences between centerfire and rimfire ammunition, along with some pros and cons, let’s discuss the 4 main rimfire cartridges available today.
.22 Long Rifle
The .22 Long Rifle, often abbreviated as .22LR or .22 LR, is what 99% of people mean when they say “I finally was able to find some twenty-two ammo.” There are still manufacturers such as CCI that make and sell the outdated .22 CB Short and .22 Long cartridges (and you can occasionally find .22 CB Caps that are ultra-short and generally comprise just primer and bullet without any gunpowder), but today these are effectively for novelty use or in specialized target-shooting platforms, or so-called “gallery rifles” of the late 19th and early 20th century. Some also use these quieter, lower-velocity cartridges for pest control. However, the overwhelming majority of .22 caliber rimfire firearms are chambered in .22 Long Rifle (even handguns), and nearly every rural store or local gun shop will usually have a good supply of .22 LR cartridges, assuming the national supply hasn’t been decimated by an ammo panic/shortage like what we’ve seen the past few years.
The .22 LR is by far the most popular cartridge in the world, with an estimated 2.5 billion rounds or more produced annually in the US alone. Its popularity is derived from its versatility in plinking, target shooting, and small game hunting, as well as its relatively low price, recoil, and noise. While top-level match .22 ammo can be more expensive than some centerfire rounds and might cost $0.45-$0.55 per round, in general, .22 LR “bulk” ammo is typically 5-10 times less expensive per round than even mass-produced centerfire cartridges like 9mm Parabellum. Additionally, the .22 LR cartridge is the only cartridge that is chambered in such a wide variety of both handgun and rifle platforms and action types.
The .22 is the only remaining holdout of a 19th-century cartridge design that uses a “heel-based,” outside-lubricated bullet where the bottom portion of the projectile is smaller in diameter than the upper portion, which is the same diameter as the outside of the cartridge case. The heel of the bullet is inserted into the case, and the exposed portion of the bullet is lubricated with wax or other suitable lubricants to prevent leading the bore. The old .44 Colt, .38 Colt, and .44 Henry Rimfire designs of the 19th century also used heel-based bullets, but only specialized/boutique reloaders or manufacturers offer the centerfire cartridges today, and nobody we know of makes the .44 Henry Rimfire. The .22 LR began life in 1887 as a black powder cartridge but was quickly adapted to the new smokeless powder loads that continue to this day.
Typical bullet weights and velocities of common .22 LR ammo include 40-grain lead bullets moving at around 1,082 feet per second, 36-grain copper-plated lead round nose (or hollow-point) bullets at about 1,328 fps in “high velocity” loads, and 32-grain copper plated lead solids or hollow-points at up to 1,640 fps in so-called “hyper-velocity” variants like CCI Stingers.
In the world of rimfire ammunition and firearms, as far as popularity and availability, the .22 Long Rifle is the undisputed king.
.22 Winchester Magnum Rimfire (.22 Mag)
When you say “22 Magnum” today, what you mean is “.22 Winchester Magnum Rimfire.” Often abbreviated as .22 WMR or .22 Mag, this cartridge is effectively the only remaining .22 magnum rimfire cartridge. (Winchester had previously offered a similar inside-lubricated, long-case design called the .22 Winchester Rimfire in 1890, and some manufacturers occasionally offer new-made ammunition for these old rifles, but no manufacturer currently chambers any firearms in this archaic cartridge.)
First developed by Winchester in 1959 and first chambered in the Marlin Levermatic rifle in that year, the .22 WMR cartridge was offered by Winchester in 1960 in their Model 61 rifle. The .22 Magnum was originally intended as a rifle cartridge for varmint control and small game hunting, but it soon was chambered in revolvers manufactured by Ruger, Colt, and Smith & Wesson, and today there has been a resurgence of various types of firearms offered in this potent little magnum rimfire caliber.
Like the .22 LR, the .22 Magnum uses a straight-walled case, but it’s quite a bit longer at 1.055” compared to the .22 LR’s 0.613” case. This means there’s more room for powder, which increases bullet speed significantly. Additionally, the .22 Magnum does away with the .22 LR’s .223” bore-diameter, outside-lubricated, heel-based bullet and instead uses a .2285” diameter standard bullet, typically thick-copper plated or jacketed.
The .22 Mag launches its bullets at pretty impressive speeds from a 24” test barrel, with a 30-grain bullet moving at 2,300 feet per second (for 322 foot-pounds of energy at the muzzle), a 40-grain at 1,875 fps for 324 ft/lbs, and a 50 grain at 1,530 fps for 300 ft/lbs. This makes the .22 WMR a fairly capable small game, varmint, and predator cartridge, as well as a possible choice for a low-recoil, high-capacity defensive cartridge for some people.
There has been a resurgence of popularity in .22 Magnum firearms over the past decade, particularly in handguns, with new offerings such as the Rock Island Armory XT series, the Walther WMP, and the KelTec PMR-30. Savage makes a delayed-blowback .22 magnum rifle, the Savage A22, which has made it possible to safely shoot the higher-pressure magnum rimfire rounds in a semi-automatic rifle platform.
.17 Hornady Magnum Rimfire (.17 HMR)
In 2002 Hornady launched a surprising new cartridge based on the .22 Magnum case but necked down to .17 caliber. The .17 Hornady Magnum Rimfire, typically shortened to 17 HMR, boasts a trajectory twice as flat as its .22 Magnum brother at 150 yards while producing around 2.5 times the energy of the .22 Long Rifle cartridge. The “17 mag” quickly found fans in the varmint and pest-control market, who found that headshots with the super-light, super-flat-shooting bullets were easy at 50 yards and reliable kills on groundhogs and similar pests were doable out to about 150 yards or so (in non-windy conditions), all with very low recoil and an inexpensive buy-in price for the firearms.
The .17 HMR can push its tiny 17-grain bullet up to an impressive 2,650 feet per second for 245 ft/lbs of muzzle energy, or a 20-grain bullet at 2,350 fps for 250 ft/lbs.
The .17 HMR is by far the most popular of the two “seventeens,” being chambered primarily in bolt-action rifles and Savage’s delayed-blowback semi-auto A17, but its baby brother (see next section) is coming back strong right now also.
.17 Hornady Mach 2 (.17 HM2)
Hornady introduced the .17 Hornady Mach 2, or .17 HM2, in 2004, and the cartridge is basically a “short magnum” rimfire, based on the CCI Stinger .22 LR case (which is slightly longer than typical .22 LR cases) necked down to .17 caliber, and firing a very light, 17-grain projectile. The “Mach 2” name is certainly influenced by marketing, but in some rifles with some cartridges at certain temperatures, it is indeed possible to double the speed of sound with this little zinger. Most rifle/cartridge combos net out about 2,000 feet per second, but some can top 2,100. The cartridge faded in popularity fairly quickly for various reasons but around 2018 several manufacturers started offering more rifles chambered for the .17 HM2, and the cartridge is experiencing a fairly strong resurgence in the market.
The key advantage compared to the larger, more powerful .17 HMR is that the .17 HM2 fits into “long-rifle” sized actions and usually feeds from the same magazines, so changing from a .22 LR rifle to a .17 HM2 usually just involves a simple barrel swap. Also, the pronounced crack of the .17 HMR is reduced a little, since the HM2 uses less powder, and it may be more reliable in feeding than the longer HMR cartridge. Depending on your retailer costs for .17 HM2 are typically a little cheaper than .17 HMR as well. Another advantage of the Mach 2 over the HMR is that the pressures produced are still within the window of reliable function in common blowback-operated semi-automatic rifles, so the mechanisms can be simpler and cheaper, identical to standard .22 Long Rifle operating systems.
With a velocity nearly double most standard .22 LR rounds, the .17 HM2 has a much flatter trajectory out to its 150-ish-yard effective range. Headshots on game-like squirrels out to 50+ yards are now possible, and the smaller, lighter projectile does less damage to meat than larger, higher-velocity centerfire cartridges.
So now you know the main differences between rimfire and centerfire firearms. As for which is best for you, that depends on your budget, your preferences, and your planned uses. In cases like this, we generally say, “Why not have both?”
Store your rimfire and centerfire guns safely with a Liberty safe
Whether you elect to use centerfire or rimfire firearms (or both), be sure to keep them secure when not in use. The best way is in a US-made Liberty gun safe or handgun vault. Check out our complete line of safes in our online catalog, or use our dealer locator to find a showroom near you.