Rimfire Misfires: Ammo, Rim Thickness or the Gun?

Safety comes before diagnosis. Once the gun is safe, the pattern of failures tells you whether to blame the box, the magazine or the rifle.

Safe first, diagnosis second

A rimfire that fails to fire is a safety event before it is a troubleshooting puzzle. The gun is loaded, the cartridge has been struck, and until you know why it did not go off you should assume it still could.

The sequence below follows general firearm-safety practice. It is not a substitute for your range's rules or your gun's manual, and where they differ, they win.

1. Keep the muzzle pointed in a safe direction. Downrange, toward the backstop, and never toward anyone. Do not lower the gun, turn to talk, or look down the bore.
2. Take your finger off the trigger. Rest it along the frame.
3. Wait. Delayed ignition, called a hang fire, is rare but documented, and the cartridge may still go off. The waiting time most often taught is at least 30 seconds. Ranges and manuals sometimes specify longer, so follow the stricter instruction that applies to you. The NSSF has published guidance on handling a gun that fails to fire, and other organizations publish similar procedures.
4. Then unload deliberately. Keep the muzzle safe while you remove the magazine if it has one, open the action, and eject or remove the round. The exact steps depend on the action: bolt, semi-auto, lever, pump or revolver.
5. Set the round aside. Do not put a dud back into a magazine. Follow the range's rules for disposing of it, and see what to tell the range officer or manufacturer.

What type of failure is it?

Different symptoms point in different directions. This table sorts the common ones.

Is it the ammunition?

A rimfire cartridge has no separate primer. The priming compound is spun into the hollow rim during manufacture, and the firing pin has to crush the rim against the edge of the chamber to ignite it. If the compound is not spread evenly or the rim is not uniform, some rounds will not fire. That is a known feature of the design, not a quirk of one brand, and occasional duds are a normal part of rimfire shooting. The Firearm Blog's rimfire reliability piece discusses the topic from the shooter's side.

Clues that point to the ammunition:

• The failure follows the box or lot. Same rifle, same magazine, different ammunition: the problem goes away.
• The strike on the rim looks normal. A deep, centered dent in the rim and no ignition suggests the round was struck properly and did not go off.
• The failures are scattered. One in a few boxes, with no pattern by magazine or position.

What you can do:

1. Set it aside and try a different lot. Record the brand and lot number of the box that produced duds.
2. Do not assume bulk ammunition is the problem. Bulk is built to a different tolerance than match, but it is also what most people shoot, and most of it fires.
3. Understand the rim. Rim thickness varies between cartridges, and that variation affects how the round seats and how the pin strikes. Our rim thickness sorting article explains why it matters for consistency. It is mostly an accuracy topic, but it also explains why some rounds behave differently from their neighbors.

Is it the gun?

Gun-side causes usually show up as a pattern rather than a one-off.

A dirty gun can create all of these. Rimfire ammunition leaves wax, lead and carbon in the chamber, on the bolt face and around the firing pin. A cleaning pass is the first and simplest test. Our cleaning kit roundup covers the tools. Excess oil is also a culprit, so use a light hand.

Is it the magazine or feeding?

Not every "misfire" is one. A round that never fully chambers cannot be struck properly. Check for:

• A bent feed lip or a weak magazine spring.
• A round sitting slightly forward in the magazine because of overlapping rims.
• A bolt not fully in battery because of fouling.

If failures follow one magazine from gun to gun, the magazine is the problem. Number your magazines and retire any that repeatedly cause trouble. Our magazines and loaders roundup covers loaders and care.

A three-step test that sorts most cases

When you are safely unloaded and have time, a short test can separate ammunition from the gun.

1. Swap the ammunition. Use a different brand or lot, in the same gun and magazine. If the failure disappears, suspect the ammunition.
2. Swap the magazine. Same ammunition and gun, different magazine. If the failure moves with the magazine, suspect the magazine.
3. Clean and retest. Same gun, magazine and ammunition after a proper cleaning. If the failure disappears, suspect fouling.

If failures persist across all three, the gun is the likely cause. Stop shooting it and have a gunsmith or the manufacturer look at it. Some defects are warranty issues, and continuing to shoot a gun with a striking problem can make it worse.

What not to do

• Do not let the muzzle drift toward people, or toward anything you do not intend to hit, while you wait.
• Do not open the action immediately to see what happened.
• Do not pull a bullet or tamper with a dud or attempt to reload rimfire ammunition. Rimfire cases cannot be reloaded safely.
• Do not fire another shot after a weak report until the bore is confirmed clear.
• Do not modify the firing mechanism yourself to cure light strikes. Springs and pins are replaceable parts a gunsmith should fit.

Keeping a record

A small log pays for itself. Write down the date, the gun, the ammunition brand and lot, the magazine number and what happened. After a few sessions, the pattern emerges: one lot, one magazine or one gun. That record is also what you will need if you contact the ammunition maker or the gun's manufacturer. Our article on dud reporting explains how.

Date-sensitive note

The guidance in this article reflects widely taught safe-handling practice as of October 2026. Waiting periods, range rules and manufacturer instructions can differ and change. The instructions for your specific range and firearm take precedence over any general article.