What Is Rimfire Ammo? A Complete Guide to Types, Uses, and Safety

What is rimfire ammo? Rimfire ammunition ignites when the firing pin strikes the cartridge’s rim, setting off the primer contained in the rim itself. This design makes rimfire rounds different from centerfire ammo, which ignites at the center of the cartridge base. Rimfire is most common in small calibers like the popular .22LR, offering lightweight, low-recoil shooting perfect for training and small game hunting.

What Is Rimfire Ammunition and How Does It Work?

Rimfire ammunition is a type of cartridge where the primer, the chemical that ignites the powder, is built directly into the rim at the base of the casing. Unlike centerfire cartridges that have a separate primer located in the middle of the cartridge base, rimfire rounds use the hollow, thin rim as an integral part of the ignition system. The firing pin in a rimfire firearm strikes the cartridge’s rim, crushing it to set off the primer compound inside. This impact causes a small explosion that ignites the gunpowder, propelling the bullet forward.

The rimfire ignition mechanism works in a straightforward way. When you pull the trigger, the firearm’s hammer hits the firing pin, which then hits the rim of the cartridge base. The rim is hollow and contains a thin layer of priming material spun or pressed into it during manufacturing. The firing pin’s strike crushes this priming layer, causing it to ignite instantly. The burning primer sends flame through the casing to ignite the powder charge. This process happens extremely fast, in just milliseconds, creating the pressure needed to push the bullet out of the barrel.

Physically, rimfire cartridges are easy to identify because the rim at the base of the casing is thicker and hollowed out to contain the primer compound. This rim extends slightly beyond the diameter of the casing body, distinguishing it from centerfire cartridges, which have a solid base and a separate primer pocket at the center. A typical rimfire cartridge includes the bullet seated at the front, a hollow brass or metal casing, the gunpowder inside, and the primer inside the rim at the rear. By contrast, centerfire cartridges have a primer cap seated in the center of the base, surrounded by a solid metal rim.

Because the primer is distributed in the rim, the firing pin must hit the edge precisely to ensure ignition. This design limits rimfire cartridges to relatively low pressures and thinner case walls. Most modern rimfire ammunition, like the .22 Long Rifle, reflects these characteristics by maintaining a lightweight, affordable cartridge suitable for target shooting and small game hunting. Rimfire casings cannot be reloaded safely or easily since the priming compound is spun into the rim during manufacturing; once fired, the rim is deformed and cannot hold fresh primer material.

In understanding rimfire ammo, it helps to picture the cartridge base anatomy: the rim forms a circular band around the cartridge’s bottom, housing the priming compound. Inside the casing is a measured amount of gunpowder, and the bullet sits at the opposite end. When the firing pin strikes this rim, it squeezes and crushes the primer inside the rim, causing ignition. This contrasts with centerfire cartridges where the firing pin strikes the central primer cap directly. This difference affects how firearms are designed to chamber and fire these rounds, influencing factors like cost, recoil, and suitable uses.

How Rimfire Ammo Differs from Centerfire Cartridges

The main difference between rimfire and centerfire ammunition lies in the ignition system. Rimfire cartridges have the priming compound spun into the rim of the case, which the firing pin crushes to ignite the powder. Centerfire cartridges use a separate primer located at the center of the cartridge base, struck by the firing pin. This distinction directly affects design, caliber options, costs, reliability, and typical uses.

Rimfire ammunition is mostly limited to small calibers, generally .22 caliber and smaller, because the thin case walls required for a rimfire design cannot withstand higher chamber pressures. Centerfire cartridges, by contrast, handle a broader range of calibers from small to large bore, supporting higher velocity and energy levels. This explains why common handgun, rifle, and shotgun rounds beyond .22 caliber are almost exclusively centerfire.

One big tradeoff is cost. Rimfire ammo features a simpler case and ignition system, making it more affordable. For instance, ranges often use popular rimfire options like .22 Long Rifle for target practice and plinking because it offers good value. Centerfire rounds have thicker, more strong cases and replaceable primers, boosting their reliability and allowing reloads, but at a higher price point. Reliability is a known downside to rimfire ammo, which can misfire more often due to the priming method and thinner case walls.

Choosing between rimfire and centerfire ammo depends on your needs. Rimfire rounds like .22LR work well if you want affordable rounds for practice or small game hunting, but expect occasional misfires and limited power. For more consistent performance, higher power, or shooting larger game, centerfire ammunition is the better choice despite higher cost. Also keep in mind that centerfire rounds are reloadable, which can reduce costs for frequent shooters who reload their ammo.

Use rimfire ammunition primarily in firearms designed for small calibers to avoid damaging the firearm or risking safety due to the cartridge’s lower strength.

Popular Rimfire Calibers and Their Applications

Several rimfire calibers remain popular today, each suited to different shooting activities based on their power, velocity, and cost. The .22 Long Rifle (LR) dominates as the most common rimfire cartridge, prized for its low recoil, quiet report, and affordability. It’s ideal for target practice, training new shooters, and hunting small game. A step up in power and velocity is the .22 Winchester Magnum Rimfire (WMR), which offers greater stopping power and longer effective range, making it better suited for varmint hunting or situations requiring more punch than a .22 LR.

The most versatile rimfire caliber is the .22 LR, favored by shooters focusing on precision, affordability, and low recoil. It suits both beginners learning to shoot and experienced shooters practicing marksmanship or plinking. The .22 WMR delivers a noticeable step up in velocity and energy. It’s preferable for small varmints such as ground squirrels or rabbits, where extra power and range improve effectiveness.

The .22 Long occasionally appears but is less common and generally offers lower velocity than the .22 LR. This round is quieter and sometimes chosen for stealthier shooting. The 9 mm Flobert remains a niche choice mostly in Europe and offers limited stopping power, best confined to indoor or short-range pest control with very low noise and recoil.

Choosing the right rimfire caliber depends on your shooting goals, budget, and desired recoil level. The tradeoff between velocity, stopping power, and ammunition cost is key. For example, small-game hunters will prioritize .22 LR or .22 WMR for their balance of power and cost; target shooters typically prefer .22 LR for its accuracy and affordability. Avoid rimfire calibers for anything beyond small game due to their inherent power limits and reliability concerns in larger calibers, which are rarely produced in rimfire form.

Why Rimfire Ammo Is Popular for Training and Small Game Hunting

Rimfire ammunition is popular for training and small game hunting because it provides an ideal balance of low recoil, manageable noise, and affordability. These factors make rimfire cartridges, especially the .22LR and .17HMR calibers, excellent choices for beginners learning basic shooting skills and small game hunters targeting rabbits, squirrels, and other similar-sized animals.

New shooters prefer rimfire ammo due to its very mild recoil compared to centerfire rounds. This low recoil helps you develop better control, focus on aiming, and reduce flinching, which often hampers accuracy in early practice. Also, rimfire ammo produces less noise, which eases shooter comfort and helps maintain concentration during extended shooting sessions. Because rimfire ammo costs significantly less than centerfire ammunition, it lets you shoot more rounds without spending a lot. This supports skill development through frequent practice without quickly depleting your budget.

For small game hunting, the moderate power of rimfire rounds delivers sufficient velocity and precision needed to humanely and efficiently take down animals like squirrels and rabbits at typical hunting distances under 150 yards. Rimfire rims provide reliable ignition in rifles designed for these rounds, allowing consistent shot placement. In contrast to larger, louder centerfire rounds, rimfire ammo limits noise disturbance to the surrounding environment, an important advantage when hunting in suburban or semi-rural areas where quiet shots are preferred.

• Low recoil helps new shooters maintain steady aim and build confidence.
• Lower noise levels reduce shooter fatigue and neighbor disturbance during practice or hunting.
• Affordable prices encourage substantial practice time and more frequent range visits.
• Effective calibers (.22LR, .17HMR) ensure ethical kills on small game at close to medium range.
• Lightweight cartridges and firearms provide easy handling for all skill levels.
• Wide availability supports consistent supply even during ammunition shortages.
• Rimfire rifles and handguns are often simpler to operate for newcomers.

To use rimfire ammo effectively as a beginner, start with simple bolt-action or lever-action rifles chambered in .22LR or .17HMR. These firearms offer straightforward operation and accuracy suitable for training and hunting small game. Regularly practicing basic marksmanship fundamentals such as grip, sight alignment, and trigger control with rimfire ammo builds a solid foundation before moving to more powerful centerfire calibers.

Invest in quality rimfire ammunition to minimize misfires, as rimfire cartridges tend to have a higher failure rate than centerfire rounds. Also, check local regulations before hunting, as rimfire ammo is usually best suited for small game due to its limited power. Choosing the right rimfire cartridge depending on your target game helps ensure effective and responsible shooting.

How to Identify Firearms That Use Rimfire Ammunition

Identifying whether a firearm uses rimfire ammunition involves checking specific markings and inspecting the barrel and chamber design. Rimfire firearms typically feature certain caliber stamps and unique firing mechanisms different from centerfire guns. Knowing these details helps ensure you use the correct ammunition and maintain safety when handling the firearm.

Check the Caliber Markings

Look closely at the barrel or frame of the firearm for stamped caliber markings. Most rimfire firearms, especially those chambered in .22 caliber such as the popular .22 Long Rifle (LR), will clearly indicate this on the barrel. Common markings include “.22 LR,” “.22 Short,” or “.17 HMR,” all of which are rimfire cartridges. Not all .22 caliber firearms are rimfire, but the vast majority of rimfire ammo is .22 caliber or smaller.

Familiar rimfire models include rifles like the Ruger 10/22, Marlin Model 60, or Smith & Wesson M&P 15-22. Checking for these markings will quickly confirm whether the firearm uses rimfire rounds.

Examine the Chamber and Breech Area

The chamber and breech design provide strong clues about the ammunition type a firearm uses. Rimfire guns have a firing pin that strikes the rim of the cartridge base, unlike centerfire guns where the firing pin hits the center primer. Usually, the firing pin hole aligns with the edge of the chamber rather than the center. To identify this:

1. Open the action to access the chamber.
2. Look for the firing pin hole’s location on the breech face.
3. Note if the firing pin hole is off-center toward the rim of the chambered cartridge.
4. Observe the thickness and shape of the barrel chamber; rimfire chambers may be slightly different due to the type of ammunition.
5. Check if the firearm has a rimfire-specific extractor or ejector design, common in rimfire firearms.

This inspection helps distinguish rimfire guns from centerfire options, even when the caliber markings are unclear or absent.

Always ensure the firearm is unloaded before inspecting the chamber or breech area to avoid accidental discharge.

Review the Firearm Manual or Manufacturer Info

Consulting the firearm’s owner manual or manufacturer website provides definitive information about the type of ammunition the gun uses. Manuals will specify either rimfire or centerfire and list compatible calibers. This information prevents misusing ammunition that could damage the firearm or cause safety issues.

If the manual is unavailable, check the manufacturer’s model number online; many companies list chambering details in product descriptions. Firearms marketed as low-cost, lightweight, and intended for training or small game hunting are often rimfire. This also applies to many .22 caliber handguns designed for target practice.

Safety Tips When Handling and Shooting Rimfire Ammunition

Rimfire ammunition requires careful attention during storage, handling, and shooting due to its design and sensitivity. Misfires happen more often with rimfire ammo than centerfire, so knowing how to respond safely is essential. Proper protective gear and safety checks help prevent accidents and maintain your rimfire firearm in good condition.

Proper Storage and Handling of Rimfire Ammo

Always keep rimfire ammunition somewhere cool and dry, out of direct light and humidity to protect its delicate casing from rust or harm. Treat the rounds gently to avoid dents, especially around the rim where the primer sits, because damage can cause firing issues. Store cartridges in their original boxes or in a strong ammo case made to shield them from impacts and deformation.

Do not try to reuse rimfire casings as they are not designed for reloading. The thinner case and primer location make them prone to stretching and damage after firing. Using damaged or reloaded rimfire cases increases the risk of dangerous malfunctions.

Safe Procedure for Misfire Situations

A misfire occurs when the firing pin strikes the rim but the cartridge does not ignite. Rimfire ammo misfires more frequently due to its primer design and thinner case. Follow these exact steps to manage a misfire safely:

1. Keep the firearm pointed in a safe direction.
2. Wait at least 30 seconds to give the cartridge time to ignite.
3. Engage the safety or unload the firearm if possible.
4. Carefully eject the misfired cartridge from the chamber.
5. Inspect the cartridge rim and casing for dents, cracks, or corrosion.
6. Dispose of the misfired round safely, do not attempt to fire it again.
7. Check the firearm’s firing pin and chamber for debris or damage.
8. Reload with a fresh round and continue shooting only after confirming safe firearm operation.

Taking these steps prevents accidental discharge and damage to your firearm. Never try to fire a second time without ejecting a suspected dud round.

Using Protective Gear When Shooting Rimfire

Always wear eye and ear protection when using rimfire firearms, just as with any gun. Rimfire cartridges still generate noise levels capable of hearing damage, especially in enclosed ranges. Eye protection guards against flying debris, hot ejected casings, and possible case ruptures, which occur more with rimfire ammo under certain conditions.

Check protective gear regularly for damage and replace worn earplugs or shooting glasses each season. Using proper equipment costs between $10 and $50 but significantly reduces injury risks during shooting sessions with rimfire ammunition.

Choosing the Right Rimfire Ammunition for Your Needs

Select rimfire ammunition by focusing on how you plan to use it, whether for target shooting, hunting, or casual plinking. Different rimfire rounds offer varying velocity, bullet types, and costs that impact accuracy and effectiveness. Picking trusted brands ensures consistent performance and safety during use.

Match Ammunition to Your Shooting Activity

Target shooting benefits from rimfire ammo that prioritizes accuracy and low recoil. The .22 Long Rifle (LR) is a common choice for both beginners and experienced shooters because it offers affordable prices and manageable shooting characteristics. For hunting small game, you’ll want a cartridge with higher energy and reliable expansion, such as the .22 Winchester Magnum Rimfire (.22 WMR), which provides more velocity and stopping power.

Plinking, or informal target practice, usually requires inexpensive ammo that functions consistently but doesn’t break the bank. Many shooters choose standard velocity .22 LR rounds for this purpose due to their low cost and availability. Deciding between subsonic, standard, or high-velocity loads depends on factors like noise tolerance and firearm type.

Consider Bullet Type and Velocity

Bullet construction significantly influences performance. Lead round nose (LRN) bullets are common and suitable for range practice and plinking, offering mild recoil and reliable feeding. Hollow point bullets are designed for hunting; they expand on impact, delivering more energy to small game. Copper-plated or plated bullets resist barrel fouling and improve feeding reliability in semi-automatic firearms.

Velocity affects both trajectory and terminal performance. High-velocity rounds in .22 LR can exceed 1,200 feet per second (fps), flattening the trajectory and improving accuracy at longer distances. Lower velocity variants reduce noise and recoil but limit effective range. The .22 WMR typically reaches velocities above 1,900 fps, making it a better choice for hunting and certain shooting sports.

• Target shooting: Use high-velocity .22 LR with LRN or plated bullets for better accuracy
• Hunting small game: Select .22 WMR or .22 LR hollow point bullets for energy transfer
• Plinking: Choose inexpensive standard velocity .22 LR rounds with lead round nose bullets
• Consider subsonic rounds for quieter shooting sessions, especially indoors
• Match ammo velocity to your firearm’s specifications for optimal reliability

Choosing the appropriate bullet and velocity helps balance cost, noise, accuracy, and effectiveness based on your shooting goals.

Recommended Rimfire Ammo Brands

Purchasing rimfire ammo from reputable manufacturers improve consistency and reliability, reducing the chance of misfires or jams. Brands like CCI, Federal, Remington, and Winchester have a strong presence in the rimfire market, offering a broad range of options suited to target shooting, hunting, and casual plinking.

CCI is known for precision and clean shooting, making it popular for competition and small-game hunting. Federal offers affordable bulk options without sacrificing performance, ideal for high-volume target shooting. Remington provides a balanced selection with some specialty rounds targeting quiet shooting and hunting needs. Winchester ammo, including .22 WMR and .22 LR, has widespread compatibility and dependable performance across firearms.

• CCI: Excellent for accuracy and clean firing; great for precision shooting and hunting
• Federal: Cost-effective bulk ammo; reliable for plinking and target practice
• Remington: Versatile lineup including quieter rounds; good for varied use cases
• Winchester: Trusted brand with options for both .22 LR and .22 WMR
• Available at specialty reloading stores like Reloading Supplies HQ and major sporting goods retailers

Prices usually range from about $0.05 to $0.15 per round depending on the caliber and ammunition type. Keep in mind that high-velocity and specialty hunting rounds generally cost more than standard target shooting ammo.

Common Rimfire Issues and How to Troubleshoot Them

Misfires with rimfire ammunition often result from the thin case walls that contain the priming compound in the cartridge rim. If the rim is damaged, corroded, or improperly struck by the firing pin, the primer may not ignite, causing the round to fail. Dirt and debris in the firing chamber or on the rim can also prevent proper ignition. Feeding problems happen when the softer case deforms during cycling, especially in semi-automatic firearms, which can cause jams or failure to chamber correctly.

Troubleshooting rimfire ammo issues starts with cleaning and inspecting both the ammunition and the firearm. Check rim edges for dents or corrosion, and avoid using visibly damaged rounds. Always store rimfire ammo in a cool, dry place to prevent deterioration. Cleaning the chamber, bolt face, and magazine feed lips regularly helps maintain reliable feeding and ignition. Inspect the firing pin for wear or damage and ensure the spring tension is adequate to deliver a solid strike.

• Misfire: Remove the round, inspect for damage, and try it in another firearm before discarding.
• Feeding jams: Clean the magazine thoroughly and check for deformed cases that might cause hang-ups.
• Light primer strikes: Clean the firing pin channel and confirm firing pin spring pressure, replacing parts if worn.
• Double feeds: Clear the chamber and magazine, then reload with fresh ammo to prevent soft case deformation.
• Corrosion on ammo: Discard rusty rounds and purchase fresh ammunition from a reputable source.
• Misaligned feed ramps: Have a gunsmith inspect and repair if necessary to maintain smooth cycling.

Routine maintenance is important for improving rimfire firearm reliability. At least every 300 rounds, strip the firearm to clean the firing pin, chamber, and bolt thoroughly. Wipe all metal parts lightly with oil to prevent rust. Use a nylon or brass brush to remove lead and carbon buildup, which can affect feeding and ignition. Check parts such as extractor and ejector for signs of wear and replace if necessary. A well-lubricated and clean firearm reduces the risk of rimfire ammo troubles significantly.

Never force a stuck rimfire cartridge; this can damage the firearm and complicate clearing malfunctions.

Step-by-Step Action Plan for Using Rimfire Ammunition

Follow this plan to get started safely and effectively with rimfire ammo in your firearm.

1. Before you start: Confirm your firearm is designed for rimfire ammo by checking the barrel markings or manual. Your firearm should function smoothly without any unusual sounds.
2. Day 1: Purchase a small quantity of the recommended rimfire caliber and brand for your firearm. Choose a popular option like .22 LR to ensure reliable performance.
3. Week 1: Practice dry firing to familiarize yourself with the trigger and handling without live rounds. You’ll know it’s effective when you feel more comfortable and steady.
4. Week 2: Load a few rounds at the range and fire slowly, focusing on safe operation and accuracy. You should notice consistent cycling and clear target hits.
5. After 1 month: Evaluate your shooting sessions and try out different rimfire ammo types for your purpose, such as higher-velocity rounds for varmints or standard velocity for target practice.
6. Ongoing: Regularly clean your firearm to prevent rimfire-specific fouling issues and inspect ammo for dents or corrosion before use. Reliable feed and firing indicate proper maintenance.

Frequently Asked Questions

Is Rimfire Ammunition Only Used in .22 Caliber Guns?

While rimfire ammo can come in various calibers, .22 is by far the most common and widely used rimfire round today, especially for target shooting and small game hunting.

Can Rimfire Ammo Be Reloaded for Reuse?

No, rimfire cartridges cannot be reloaded because the primer is in the rim, which is crushed during firing and not replaceable.

Why Is Rimfire Ammo Usually Cheaper Than Centerfire Ammo?

Rimfire ammo is less expensive because its primer design and smaller casing are simpler and cheaper to manufacture compared to centerfire rounds.

Is Rimfire Ammunition Suitable for Self-Defense Purposes?

Rimfire ammo is generally not recommended for self-defense due to lower power and reliability compared to centerfire ammo.

How Does the Quality Vary Among Rimfire Ammo Brands?

Quality can vary, affecting reliability and accuracy; testing different brands helps find the best option for your firearm.

Are Rimfire Guns and Ammo Used by Law Enforcement or Military?

Rimfire ammo is mostly for training and small game hunting, not for law enforcement or military uses which prefer centerfire rounds.

The Bottom Line

Rimfire ammunition offers a simple, affordable way to learn shooting and handle small game hunting with a variety of user-friendly calibers. Start by choosing the correct ammo and firearm combination, then practice safety and maintenance for the best experience. Head to the range with your preferred rimfire rounds and focus on steady, controlled shooting to build your skills.