What Is a Rimfire Rifle and How Does It Work?

Inspect the cartridge rim to understand how rimfire ignition works

To understand what a rimfire rifle is, look closely at the ammunition it feeds. A complete round of ammunition is called a cartridge. Every cartridge contains four main parts: the outer metal case, the gunpowder sealed inside, the bullet seated at the top, and the chemical primer mix that sparks when struck to ignite the powder.

In standard centerfire ammunition, that primer sits in a small, separate metal cup pressed into the dead center of the case base. Rimfire ammunition works differently. There is no separate cup in the center. Instead, the manufacturer spins the liquid chemical primer mix outward so it packs directly inside the hollow, folded outer rim of the brass case.

When you load a rimfire rifle and squeeze the trigger, an internal spring drives the firing pin forward. The firing pin is a small steel rod with a chisel-shaped or flat striking tip. Instead of hitting the middle of the cartridge base, it strikes the soft outer edge of the rim.

That strike pinches the brass rim flat against the hard rear edge of the rifle chamber. That sudden crushing blow creates an immediate internal spark. The spark instantly ignites the gunpowder packed inside the casing, creating rapidly expanding gas.

Because that expanding gas has nowhere else to go inside the sealed metal chamber, it builds tremendous pressure. It pushes the lead bullet out of the casing, guides it down the spiral grooves inside the barrel, and sends it flying toward your target. It is a simple, proven mechanical design that gunmakers have used reliably for well over a century.

Never confuse a powder firearm with an air rifle for practice

New shooters often confuse rimfire rifles with air rifles because both platforms frequently use .22 caliber ammunition. Caliber simply describes the diameter of the barrel and the projectile, measured in hundredths of an inch. A .22 caliber rimfire bullet and a .22 caliber air rifle pellet are roughly the same width, but they operate on completely different principles.

An air rifle uses mechanical air pressure to push a shaped lead or alloy pellet. Break-barrel rifles are cocked by pivoting the barrel down to compress an internal spring or gas piston. Other airguns rely on disposable gas cartridges or pre-charged pneumatic reservoirs filled with high-pressure air from a special hand pump or compressor. They burn no gunpowder, produce no hot gas, and generate significantly less energy.

A rimfire rifle is a genuine firearm that burns gunpowder. When that powder ignites, it generates explosive chamber pressures and launches a solid lead bullet with lethal force. A standard .22 caliber rimfire cartridge produces roughly 100 to 140 foot-pounds of energy at the muzzle. Most standard .22 caliber pellet airguns generate between 15 and 30 foot-pounds of energy. That means a rimfire bullet hits with many times the punch of an ordinary pellet.

Noise levels also set these tools apart. An air rifle equipped with built-in noise baffles or muffled barrels produces a mild pop or dull thud that rarely disturbs neighbors. In contrast, even a modest rimfire cartridge creates a sharp gunshot crack that exceeds 140 decibels and demands ear protection. If you want casual target practice on a typical residential lot, an air gun for backyard plinking is built for that setting, whereas discharging a powder firearm in town can quickly trigger panic and police calls.

Learn the difference between rimfire and centerfire cases before buying ammo

When you browse the ammunition aisle at a sporting goods store, you will see two broad categories: rimfire and centerfire. Knowing how to tell them apart keeps you from buying the wrong box and helps you understand what your rifle can handle.

Centerfire cartridges have thick, sturdy brass walls and a distinct circular primer pocket pressed into the exact center of the base. You find centerfire designs on handguns, shotguns, and large hunting rifles. Because the brass case has thick walls, it can withstand massive pressure from large powder charges.

Rimfire cartridges must have thin, soft brass rims. If the brass at the base were thick and rigid, the rifle firing pin could not crush the rim enough to ignite the internal primer compound. That thin brass creates a hard physical limit. If a manufacturer loaded a heavy powder charge into a rimfire case, the extreme pressure would blow out the rim and spray hot gas into the action. Rimfire designs are therefore limited to lower pressures and smaller bullets.

That design difference also affects how you handle empty brass. Many target shooters save empty centerfire brass cases, press out the spent primer cups, and reload them at home with fresh powder and new bullets. You cannot reload rimfire brass cases. Once the firing pin crushes and dents that outer rim, the case is permanently warped and cannot be primed again. Once you shoot a rimfire round, the spent brass goes into the scrap bucket.

Match your rimfire caliber to your target size and shooting distance

Rimfire rifles come in several distinct calibers, each tailored for specific chores. Selecting the right caliber ensures you have enough punch for your target without wasting money on overkill.

The .22 Long Rifle, commonly written as .22 LR, is the undisputed king of rimfire shooting. It has been around since the late 1800s and remains the most popular cartridge on earth. It produces virtually zero shoulder recoil, costs very little per shot, and delivers pinpoint accuracy out to 50 or 75 yards. It is the go-to round for paper targets, metal spinners, and controlling small pests like rats or squirrels.

The .22 Short is an older, much smaller cousin of the .22 LR. It holds a tiny powder charge and a lightweight bullet. Because it burns so little powder, it produces very mild noise and modest energy. Shooters occasionally use it for close-range pest control or old-fashioned gallery target games, though many modern rifles are not chambered for it.

The .22 Winchester Magnum Rimfire, or .22 WMR, steps up the power significantly. It features a longer, wider brass case loaded with extra gunpowder. A .22 Magnum pushes its bullet significantly faster than a standard .22 LR, delivering over 300 foot-pounds of muzzle energy. That added reach and punch makes it effective for larger varmints like groundhogs, raccoons, and foxes out to 100 or 125 yards.

The .17 Hornady Magnum Rimfire, known as .17 HMR, takes a .22 Magnum case and narrows the neck down to hold a tiny .17 caliber bullet. That lightweight projectile exits the muzzle at blisteringly fast speeds, often topping 2,500 feet per second. It shoots in a very flat path with almost no bullet drop at 100 yards, making it deadly on prairie dogs and crows in windy open fields.

Check local firearm laws and build a true backstop before shooting

Because a rimfire rifle feels light and produces minimal recoil, beginners sometimes make the dangerous mistake of treating it like a backyard toy. It is a genuine firearm, and every shot demands strict safety habits.

Check your municipal and county ordinances before unzipping a gun case. In nearly all suburban cities and incorporated towns, discharging any powder-burning firearm is strictly prohibited by law. Even if you have several acres, county codes often dictate minimum distances from roads, schools, and neighboring homes. Violating these laws can lead to criminal charges, weapon confiscation, and steep fines.

Never underestimate how far a small bullet can travel. The warning printed on nearly every box of .22 LR ammunition states that the bullet is dangerous up to one and a half miles. If you miss your target or shoot upward at a pest in a tall tree, that bullet will arc over the treetops and maintain lethal speed as it falls back to earth.

Always shoot into a verified, solid backstop. A wooden privacy fence, a stack of firewood, or a sheet of plywood is completely inadequate. A standard .22 LR bullet will punch clean through two wooden fence boards without slowing down. A safe backstop must consist of a thick earth berm (a high dirt mound free of rocks), a steep natural hillside, or a certified heavy-gauge steel bullet trap designed specifically for firearms.

Protect your eyes and ears every single time you head to the range. While a rimfire rifle does not kick your shoulder, the sharp blast can cause permanent, cumulative hearing damage over time. Quality eye protection shields you from hot propellant blowback, lead shavings, and rogue ricochets.

FAQs

Can dry firing damage a rimfire rifle?

Yes, dry firing can damage many rimfire rifles. Dry firing means pulling the trigger with an empty chamber. Because there is no soft brass cartridge rim in the chamber to cushion the blow, the hardened steel firing pin strikes the steel edge of the chamber directly. Over time, this repeated impact can peen or notch the chamber opening and chip or break your firing pin. Always check your rifle manual before dry firing, or use plastic snap caps to safely absorb the strike during trigger practice.

Is a rimfire rifle suitable for home defense?

A rimfire rifle is generally not recommended for home defense. While a .22 rimfire bullet can certainly cause lethal wounds, it lacks the immediate stopping power needed to stop a determined threat quickly. Rimfire ammunition is also less reliable than centerfire ammunition because the priming compound is spun into the rim mechanically, which can occasionally leave empty spots that cause misfires or duds. A dedicated centerfire firearm is far more dependable when personal safety is on the line.

Why is rimfire ammunition so much cheaper than centerfire rounds?

Rimfire ammunition costs significantly less because the manufacturing process is much simpler. A rimfire case is stamped from a single piece of thin brass, and the priming compound is poured directly into the hollow rim cavity. Centerfire cartridges require separate metal primer cups, tiny internal anvils, and precisely drilled flash holes in the base. The smaller powder charge and lighter lead bullets used in rimfires also cut down on raw material costs, keeping prices low for high-volume target shooting.

Can you shoot .22 LR ammunition in a .22 Magnum rifle?

No, you should never attempt to fire .22 LR ammunition in a rifle chambered for .22 WMR (.22 Magnum). Even though both cartridges fire bullets of similar diameter, the .22 Magnum case is noticeably wider and longer than a .22 LR case. If you place a .22 LR round inside a .22 Magnum chamber, the loose cartridge will fit poorly, causing the thin brass case to split or rupture upon firing. That rupture can blow hot gases and burning powder backward into the rifle action and toward your face.