Causes
Rimfire priming is a primitive system with inherent weaknesses. The big weaknesses are weatherproofing, crush protection and vibration.
The only protection against liquid contamination is the outside coating of bullet lube. The ring of primer compound is protected by a thin layer of cartridge brass. The compound itself is basically glued into the rim cavity of the cartridge with the binders that hold the compound together. Too much shock or vibration can cause a piece of the compound to dislodge from the cavity and if that’s where the firing pin hits, you’ll get a click instead of a bang.
Excessive head space will cause insufficient support for the “hit” to happen that’s required for the rimfire reliability. The result will be a light hit. Head space increases after years of wear.
The chamber mouth or firing pin can also be deformed from dry firing or carless application of a steel cleaning rod, these also reduce rim support.
The rimfire priming system requires precise placement of the firing pin strike on the case rim. If the firing pin drifts, due to lateral play, or wear or poor tolerance it will cause a misfire. Wear or damage to the tip of the firing pin will also cause misfires.
Semi-automatic rimfire rifles and pistols can also misfire from too much debris and too few cleanings. The area where the bolt seats must be reasonably free of debris, an accumulation here can stop the bolt before it is fully “home” requiring the firing pin to reach farther.
Cures
Most of the causes cited are easy to check. Even head space problems, but you can’t check everything. A dirty or damaged firing pin spring in a rifle may be hard for the end user to access, so get a Professional Gunsmith to check it out.
If I get a gun from a customer that’s misfiring, I check the gun first, then I move to the ammo. Some guns just don’t like certain ammo.
Personal Note
Because rimfire cartridges do have an inherit weakness to misfire, some people will not carry a firearm with rimfires for personal protection…. Reliability is kind of important in a self-defense situation.
Be safe out there.
