The free floating firing pin strikes the primer every time the chamber is loaded, although normally not with enough force to fire the round, until it does. Keep the muzzle pointing in a safe direction.
During a class this week a student’s pistol experienced a couple of “slam-fires.” Twice, during an empty reload with a Browning Hi Power, the pistol fired when he cycled the slide to chamber a round. I was watching him carefully – we had just started working on empty reloads and I was watching him carefully - so I know his finger was nowhere near the trigger when this occurred. The pistol was pointing downrange – we teach students to keep the muzzle on target during reloads - so there was no danger. Slam fires are not uncommon, and an important reason to always keep the muzzle pointing in a safe direction during all manipulations.
The pistol in question had been modified. It had a trigger job done by a gunsmith. In order to get a lightweight, crisp trigger ‘smiths will often cut the tolerances too close on the hammer and sear, and/or lighten up spring pressures on the trigger components. Cutting and fitting everything to these tolerances will produce the desired feel. But often it’s usually not long before things wear, and the hammer starts to jump or follow the slide forward as it cycles. The result is an unintentional discharge. This would be different from a negligent discharge, which results from the finger being on the trigger at the wrong time. (Although technically this is a form of negligence since the weapon has been modified to the point it is unsafe.)
Be very careful when it comes to modifying a trigger. First, make sure the gunsmith you’re using is qualified to perform the work you’re looking for. Work that’s performed improperly is dangerous to you and anyone else around you. It can lead to slam fires, plus for defensive purposes a trigger that is too light is simply dangerous. Under stress you’ll end up firing an unwanted shot; this is especially true when attempting to reset the trigger after firing a shot. A light trigger also potentially opens you up to some serious legal problems.
Slam fires will occur with long guns too. The AR, AK, SKS, 870 shotguns – and most other long guns – have a free-floating firing pin. This means that every time a round is chambered the firing pin hits the primer. Normally it doesn’t striking the primer hard enough to ignite and fire a round. But, if you have a faulty round, or a high or sensitive primer the weapon can fire when chambering a round. This is true while firing and when manually loading or reloading. And yes, slam fires will occur with bolt-action rifles as well.
A dirty firearm can also cause slam fires. When too much grime builds up in the channel for the firing pin it prevent can the firing pin from traveling freely. If the firing pin locks up in a forward position it can cause a slam fire.
The possibility of a slam fire means when you’re manipulating your weapon – loading, unloading, reloading or clearing stoppages - the muzzle should pointing in a safe direction. For administrative manipulations – loading, unloading or checking its status – the muzzle should be pointing downward and at something that would stop or trap an errant round. During reloading or clearing a malfunction the muzzle should be on target, so if a slam fire does occur the round is going downrange.
Owning a firearm is about responsibility. Buy good equipment. Be careful when it comes to modifications. And always keep the muzzle pointing in a safe direction.
Tiger McKee is director of Shootrite Firearms Academy, located in northern Alabama. He is the author of “The Book of Two Guns” - http://shootrite.org/book/book.html writes for several firearms/tactical publications, and is featured on GunTalk’s DVD, “Fighting With The 1911 - http://shootrite.org/dvd/dvd.html McKee’s new book, AR-15 Skills and Drills, is available off Shootrite’s website: http://shootrite.org/AR15SkillsBook/AR15SkillsBook.html