A malfunction, sometimes also referred to as a stoppage and often shortened to malf, is when a firearm doesn't function as intended. This can be caused by almost anything, but the most common causes are improper assembly, improper lubrication, weak springs, an overly dirty weapon, and parts breakage.
More rarely, a cartridge may explode when fired, causing what is known as a "kaboom" or "kB". This is generally due to overpressure, which has several causes: too much powder, the wrong kind of powder, bullet setback (when the bullet is seated too far into the case), and excessive heat. Kabooms (the weapon exploding) also tend to happen when a round fires out of battery, or a case is not properly supposed by the chamber and ruptures.
Types of malfunctions
Malfunctions are classified by cause.
- Failure to fire (FTFire, Type 1): Can be caused by a weak or broken hammer spring. Can also be caused by a clogged firing pin channel, especially in striker-fired firearms, or a misaligned striker failing to properly impact the primer.
- Failure to extract (FTExtract, Type 3): Extractor does not pull spent casing from chamber; can be caused by a weak extractor spring, worn extractor claw, or a dirty chamber.
- Failure to eject (FTEject, Type 2): Spent casing is not completely ejected from firearm; can be caused by a weak/broken ejector spring.
- Stovepipe: Specific type of failure to eject where the action closes on the casing before it has left the weapon, leaving it sticking out in a manner resembling a stovepipe. Can be caused by errors in the design of the ejection system, a faulty ejection system, or faulty ammunition.
- Failure to lock (FTL)
- Failure to chamber
- Failure to cock: Hammer does not stay cocked back.
- Doubling/bursting: Semi-automatic firearm firing more than one shot per trigger pull. Usually caused by problems with the sear.
- Double-feed: Weapon strips multiple rounds from the magazine during a single cycle of function. Usually caused by design flaws in the weapon, improper components or flawed magazines.
- Slamfire: Weapon fires upon being chambered. Firing pin may be stuck, or free-floating firing pin may have detonated the primer. Can occur on older pump-action shotguns if the trigger sticks.
- Runaway fire: Fully-automatic weapon fails to cease firing when the trigger is released. Usual cause is the sear sticking or otherwise failing to re-engage.
- Cook-off: Specific runaway fire state where ammunition is triggered by heat upon being chambered. Caused by excessive heat build-up in the chamber from prolonged firing.
- Burst barrel: barrel splits open during firing. Usually caused by metallurgical flaws in the barrel, or an object lodged in the barrel.
- Burst chamber: chamber cracks or splits on firing. Usually caused by subjecting the weapon to extreme temperatures, or metallurgical flaws.
- Slide separation: Slide of a semi-automatic pistol is not retained and leaves the frame. Usually caused by excessive wear, use of overpowered ammunition or design flaws.
- Bolt separation: Bolt of a bolt action rifle fails to lock and shoots back to its rearward position or completely clear of the weapon on firing. Can be caused by severe wear, misassembly or use of overpowered ammunition.
- Failure to feed (FTFeed): Bolt or slide does not pick up next round, or picks up next round but does not feed it into the chamber. Often caused by a bad magazine spring, bent/broken feed lips, or the magazine not being inserted all the way into the firearm.
- Failure to fire (FTFire, Type 1)
- Failure to ignite: Primer does not detonate; primer ignites, but propellant does not burn
- Case head separation: Extractor pulls the back off the case off and the rest of the case remains in the chamber. Caused by weakened case walls, or a cycle that is too fast and attempts to extract the case while gas pressure is still retaining it.
- Case rupture: Case wall bursts during firing. Can be caused by a poorly designed chamber that does not properly support the case, out-of-battery firing, or by manufacturing flaws in the cartridge.
- Failure to feed: In gas-operated firearms, this can be caused by the burning propellant not producing enough gas pressure to completely cycle the firearm. In recoil-operated weapons it can be caused by under-loaded ammunition.
- Failure to extract (FTExtract, Type 3): Can be caused by dirty ammunition.
- Slamfire: Can be caused by a soft primer.
- Hangfire: Delay between the weapon operating and the round being fired. Caused by manufacturing errors in the ammunition. Standard safety procedure is to assume any weapon that completes a proper cycle of function but does not fire is experiencing a hangfire.
- Squib load: caused by a insufficient powder load, leading to a round stopping in the barrel. If the squib is not removed and another round is fired it will cause a catastrophic failure.