Rimfire vs. Centerfire Ammo: A Comparison

For some people in the shooting community, choosing ammunition — especially for home defense — can be a little daunting. There are a lot of bullets out there – which makes for a steep learning curve, especially when it comes to teasing out the relative strengths of smaller calibers. These different types of ammunition can differ in the manufacturing process, bullet design, and performance (which makes us all thankful for ballistics gel tests). 

To help you wade through the right information you’d need to pick the right ammunition for you, we’re going to take a deep dive into two types: rimfire and centerfire ammunition.

Bullets, A Primer

Bullets have come a long way since their inception. Before ready-to-fire cartridge-based ammunition was invented, you’d have to stuff black powder, wadding, and a ball down the bore with a stick, then attach a percussion cap to the right spot, hold your breath, and hope that the trigger — which was a modified clock mechanism — would do its job. 

50% more reliable than early firearms

Ammunition as we know it today came about in 1808 with the Swiss gunsmith Jean Samuel Pauly’s integrated “needle-fired” round. Various innovations up and through 1846 finally saw Parisian gunsmith Benjamin Houllier patent more effective (and ultimately similar to today’s ammunition) rimfire and centerfire cartridges.

Those 1800s-era cartridges had cases that were made of a variety of period-specific materials – including paper, bronze, brass, and tin. Today, the most popular case is typical “yellow” brass but you can certainly encounter materials like nickel, aluminum, and steel depending on the cartridge case, price, and intended purpose.

On one end of the case sits a bullet that will eventually be propelled down the barrel. Opposite that bullet is the primer, creating a self-contained round that has all you need in a single package.

Self-contained metal cartridges are substantially more wear- and weather-resistant than the individual components. Not to mention faster to reload and considerably more convenient to pack around. 

In addition to the additional convenience and durability the cartridge-based round also introduced much more consistency in manufacture, increasing reliability and unlocking innovation that has allowed almost every different caliber of round to become better over time.  All bullets are fired the same way – a striker or a hammer hits and ignites the primer, which detonates the powder and sets off a small explosion, forcing the cartridge to expand, sealing the chamber, and sending the bullet on its merry way. Both rimfire and centerfire cartridges work this way. There are some big differences, however, when it comes to the primers.

Generally, rimfire cartridges work exactly as described above. What makes them special is — as you might infer by the name — the primer extends all the way to the rim of the cartridge. The firing pin strikes that rim to fire the round. Like any type of technology, this has some pros and cons.

In terms of pros, the manufacturing process requires less precision, making rimfire ammunition more affordable than precision cartridges with tighter tolerances. That’s one of the reasons almost every firearm enthusiast has at least one .22LR gun: you can afford to shoot them all day. 

They also tend to be used in small caliber firearms with lower pressure rounds because the wall of the cartridge has to be thin enough to be crushed by the firing pin. This makes rimfire firearms great for training new shooters thanks to their miniscule recoil.

As for the cons, the biggest two are reliability and magazine loading. Because rimfire ammo is manufactured with — uh — generous tolerances it can also be inconsistent. 

That said, quality ammo is still affordable and will almost certainly work well for most firearms. 

Rimfires also have a larger base rim than their centerfire counterparts: which prevents them from stacking well in a vertical orientation. This can create feeding issues in magazines, so you’ll generally see .22LR rifles with rotary magazines, which are slow to reload and limit capacity to about 10 rounds. 

When it comes to price-per-round the .22LR reigns supreme as it’s easily the most affordable cartridge available. This factor alone will keep this little rimfire champ in circulation for the foreseeable future.

.22LR This is, for most folks, the first round they ever fire. It’s cheap, easy to find, has virtually no recoil, and is perfect for learning how to shoot. The .22LR has come a long way since hitting the market in 1884 – offering more reliability and variation over the years, with it now being the go-to round for varmint hunting. It’s awfully hard to top the fun of spending an afternoon plinking through 500 rounds with a Browning SA22 for just a few bucks.

.17 HMR. A newer entry into the rimfire universe, the .17 HMR – or Hornady Magnum Rimfire – was developed in 2002 by necking down a .22 Magnum case to the smaller .17 caliber. The 17 grain projectile rips along with a muzzle velocity of around 2,600 ft/sec, or about 50 faster than a typical .22LR round. This makes it an outstanding varmint hunting and target shooting round out to a few hundred yards.

Centerfire rounds work on the same general principle as rimfire, except the primer is independent from the case and press-fit into the rear of the round. This primer is struck by the firing pin, setting off the chain reaction resulting in a round being fired. Centerfire rounds have a tighter rim-to-casing ratio, enabling them to stack more efficiently in magazines than rimfire rounds. Additionally, this design means that much higher pressures can be achieved, which is why basically all larger caliber rounds are centerfire. They can also be reloaded with relative ease, making them a popular choice with reloading enthusiasts & thrifty shooters.

Centerfire rounds have more components, which means they cost more to make and, in-turn, shoot.

The .40 S&W. is the 40 cal big brother to 9mm, meant to bridge the gap between the size of the 9mm and the classic .45ACP. This round is an excellent, if now a little niche, defensive handgun round that packs considerable stopping power. Any semi-automatic handgun in .40 S&W or 9mm is an excellent carry choice.

There’s some debate between the two and while the .40 S&W has more energy and superior ballistics, the 9mm is a more than capable round in its own right thanks to additional carry capacities and lower recoil. 

5.56mm. The 5.56mm demonstrates the difference between rimfire and centerfire cartridges well. Despite a bullet with roughly the same diameter as a .22LR rimfire, this round packs a lot more pressure behind the bullet, and thus is effective at combat out to 500 yards or so in skilled hands. Other fantastic examples of centerfire rifle ammunition include the big brother to the 5.56, the 7.62×39, the classic .308, and AR-15 pistol-friendly .300 BLK.

Regardless of if you’re shooting rimfire or centerfire ammo, there are lots of great options out there. And what you choose should ultimately be informed by your use case and what you hope to achieve with it.

• Roy Chesson, Rimfire vs Centerfire: Which is Better for You?, April 22, 2019
• Wikipedia article, Rimfire ammunition
• Wikipedia article, Centerfire ammunition
• Wikipedia article, .17 HMR
• M Carbo, 17 HMR vs 22LR
• gundata.org, 17 HMR Ballistics Chart & Drop Table
• detecting.us, Civil War Bullet Reference Guide
• LuckyGunner, .22LR Ballistics Gel Test