Firing Pin Logic and Mechanics

If there is an overlooked part in any firearm, it is the firing pin. The firing pin is an important part of ignition and also has a bearing on accuracy and lock time, yet shooters seldom think of it unless it breaks or gives trouble. There are also safety concerns with certain types of firing pins if the shooter isn’t schooled in floating firing pins. Recently I was entertained to a story about a customer who brought a rifle into a pawn shop.

Let’s just say he isn’t a common gun owner and is of the type we could probably do without. He brought in a padded case containing an AR-15 rifle to pawn or sell. The shopkeep asked if the gun was loaded and the fellow replied that he didn’t think so. While wrestling the rifle from the case, he dropped the still-loaded magazine. My friend Gene took over, pulling the charging handle to the rear while keeping the muzzle pointed in a safe direction to clear the rifle— which ejected alive round!

We won’t go into the problems with keeping a rifle chamber loaded in the home or the idiocy of bringing the piece into a shop loaded, but something else was curious. The cartridge extracted from the chamber had a distinct firing pin indent. Gene wondered how that happened. To told him to count the rounds in the magazine, betting there were thirty. There were.

The only answer I have is the fellow had hand-fed a cartridge into the chamber and let the bolt slam, resulting in a firing pin mark on the primer from the floating firing pin. While we know not to load an AR or M1A in this manner, not everyone does. This fellow was lucky and his poor gun safety is an accident waiting to happen. I know the difference between different types of firing pins and how they work.

As I have dealt with firing pins I have developed a healthy respect for their function and the need to learn more about them. But I am still learning. A problem with firing pins doesn’t become evident until we pull the trigger and nothing happens. We hear a click instead of a bang. This is pretty serious in a personal defense firearm and bad news in competition. Many shooters look to the ammunition first and don’t search for a potential mechanical failure.

While this seems obvious to some it isn’t always the ammunition. In my experience the cause of a failure to fire is just as often a dirty chamber or a problem with the firing pin. There are many different types of firearms and firing mechanisms but they have some type of firing pin or striker. The firing pin strikes the primer and forces the outer shell of the primer against an anvil inside the primer which sparks, igniting the priming compound and then the powder.

This is pretty simple and it occurs in a millisecond but all of those moving spring-loaded parts have to be properly in specification and must strike the primer with enough force to crack it. The action is more involved than the cartridge and with more parts. The cartridge has to fire but once while the firing pin will be cycled thousands of times.

Transfer Bar Problems Transfer bar systems were introduced as early as the turn of the twentieth century in the old Iver Johnson and Hammer-the-Hammer transfer bar safety system. They are usually quite safe and reliable. When they were first incorporated into heavy revolvers such as the Charter Arms Undercover and Ruger Security Six some shooters felt that the system might not prove Far

as accurate as the conventional firing pin mounted in the hammer. Locktime, along with a clinging to tradition, was the concern. Considering the accuracy of the Ruger GP100 these fears are groundless, although mass production does sometimes present difficulty. There are occasional problems with the hammer contacting the transfer bar or frame too soon, resulting in a misfire or failure to fire. This isn’t that difficult to diagnose.

It seems like every time this occurs the shooter mentions the rate of failure is very small, sometimes one in a hundred, and it sometimes gets passed off as bad ammunition or a high primer. This isn’t a valid assumption if the problem reaches a 10% misfire rate. It is easy enough to cure this problem. Take about 0.020 off the hammer at the point the hammer strikes the frame.

This isn’t necessary if the revolver is properly firing but is often the cure for an occasional failure to fire with a transfer bar type revolver. I have yet to see this problem on a single action revolver, foreign or domestic, only double action revolvers. On the subject of double action revolvers, the firing pin design of the Colt Python and the earlier Colt Three Fifty Seven is such that the revolver should never be dry fired. By the time it arrives at the shop it is too late.

Without getting into a discussion into primers—and I handload CCI, Federal, and Winchester primers with good results—sometimes a firearm will fire fine with one make and not another. Some primers are thicker, which is needed with Magnum pressure. The bottom line—do you want a firearm that won’t crack every primer? You do not know which primer the factory loads and most giant makers use several types. Occasionally, congealed oil and solvent in the firing pin channel may cause a problem.

This mixture looks like varnish in some firearms. A lack of cleaning and maintenance and perhaps a dirty powder or even lead residue makes this mixture. A simple cleaning is often sufficient to get rid of the failure to ignite the primer. I have actually observed broken firing pins that still ignited firearms, something that is more likely with two piece firing pins; I have seen several and heard of a few more. This isn’t a good thing and eccentric wear often is the result. Keeping things clean helps.

There are other causes of light primer strikes, primarily related to self loading handguns. I probably see ten self loaders for every revolver these days, so I see more issues with these firearms. There are also ARs and bolt action rifles as well. In older military rifles there is a possibility that very excess headspace will cause problems, though more often a blunted, damaged, or off-spec firing pin is a problem. The firing pin may be below the minimum measurement for firing pin protrusion.

Hard primers area possibility but unlikely with While it is difficult to observe and gauge, springs become worn.

The bolt assembly houses the firing pin and problems related to ignition are often contained in the bolt. If it hangs up, locktime is slowed. American-made ammunition. A number of years ago a local agency purchased several thousand rounds of cheap Egyptian surplus 9mm Luger, which proved to be a very bad move by an inexperienced instructor (there are many personnel in instructor roles whose total experience is limited to a school lasting a few weeks).

In their SIG pistols this ammo had a 50% failure rate and 25% in their Beretta 92s. Even worse, by the time I was asked to examine the pistols they were rusting from the corrosive priming compounds. A weak or completely broken firing pin can be a problem or even improper assembly, but very occasionally it is actually the ammunition. The floating firing pin I mentioned with the AR-15 pawn shop incident should be understood. The M1 Garand and M14/M1A have floating firing pins.

The design works well and is Far safe when the rifles are used properly. The magazine or en bloc clip is locked in place and the bolt ran forward. This slows the bolt down due to loading the cartridge from the magazine or en bloc clip. If the cartridge is single loaded loose and the bolt dropped forward on it, the floating firing pin will run forward harder and make an indent in the primer. I have never actually seen a rifle fire in this manner but I am certain it has happened.

This is why competitors use harder CCI rifle primers. Even when firing a few rounds at targets and during evaluations these rifles should always be loaded from the magazine. If you inspect a rifle cartridge that has been chambered and then extracted without firing it is normal to see a slight dimple from the floating firing pin, although this varies with different makes and types of rifles. It is of no concern.

A dimple from dropping a loose round in the chamber and then dropping the bolt will be deeper from lessened resistance and friction, and by extension can be more dangerous. There are many types of firing pins. Some are so thin that it appears as if they would be easily broken but are hard tempered and durable. They are not always perfectly straight and some have noticeable angles. With this understood it is easy to see why the firing pin and inconsistent movement may cause a problems with accuracy.

Congealed powder and ash in the firing pin channel may result in inconsistent ignition. The cartridge may be pushed a bit into the chamber with one strike and barely struck with another. This

Neither presents much of a difficulty for a properly in-specification firing pin and action. has been heavily greased and in longterm storage we clean the firing pin channel as well as possible. If the firing pin channel is gunked up and the firing pin has to fight to get through, cannot be good for accuracy, especially in rifles. We know that if the revolver hammer contacts the frame as it falls, accuracy or ignition will be a problem. Correcting hammer side play solves this problem neatly.

I’ve experienced another problem from the direct result of inconsistent firing pin energy. A Smith & Wesson Model 5906 9mm had began to group badly for an in service officer, so badly he nearly failed to qualify at 25 yards. There seemed to be no apparent problem until I did a detail strip and found brass shavings in the firing pin channel. Could this be the problem? After the channel was properly cleaned and the firing pin replaced the pistol returned to its original accuracy potential.

I am certain the same could occur with a badly weakened firing pin spring. This is the reason that when we clean a military rifle or any firearm that The new design Python should not have the same problem in dry fire but only time will tell. ignition simply can not be consistent. A firearm with mediocre to fair accuracy may see some improvement with this simple cleaning; it will certainly be more reliable.

Summary In my experience, even weak firing pin springs and inconsistent actions will set off primers but a good, sharp firing pin and a properly set up, clean action will be the most efficient and demonstrate best accuracy. Spring rates matter. I have even considered cocking piece drag, which exists but is seldom a concern save for those in the higher strata of shooters. In general, the better the firing pin is supported during its entire travel the less trouble you will have.

There is nothing you can do to change the design other than to be aware of it but you may be able to polish the breech face and keep the firing pin channel clean and eliminate most problems. AG