AR-15 Firing Pin

There have been some AR-15 owners who, when they take the rifle apart, find no spring around the firing pin and wonder if their rifle is missing a part.

From the time the M-16 Rifle was first adopted by the U.S. military and was offered to civilians in an AR-15 semi-auto version, it has been popular with the American public. Interestingly, the AR-15’s popularity rises and falls in almost predictable cycles, but becomes more popular during periods when Americans perceive a threat to their Second Amendment rights.

This isn’t a political column, but the reasons people have almost bought out many gun shops’ inventory of AR-15 rifles at times is interesting to study.

Many people who have bought AR-15s the last few years have done so without realizing exactly what an AR-15 is, how it works and how to disassemble it for cleaning.

Most of my friends who have served in the military know their AR-15s intimately and even have named them after their favorite girl or favorite girl’s name, which if they know what is good for them is the same as their wife’s name.

However, I have had a few friends tell me that they bought an AR-15 and would like me to run them through how to disassemble it and more importantly, how to put it back together. If you have friends like that, and you are familiar with the AR-15, be nice and spend some time with them. Not everyone can pick up the procedure just by reading the instructions. It is always nice to have an expert show you how to take care of your rifle.

For instance, an issue I see with AR-15 owners quite often concerns the use of a free-floating firing pin. There have been some owners who, when they take the rifle apart, find no spring around the firing pin and wonder if their rifle is missing a part, which will make the rifle susceptible to slam fire when chambering a round.

During early development, Eugene Stoner intended the firing pin to be free floating, but others convince him to try a light spring around the firing pin. The firing pin spring was rejected and it was left as a free-floating firing pin because the titanium firing pin is so light, it doesn’t develop enough energy to fire the cartridge during the chambering of a round, or if the rifle is dropped.

The AR-15 has a hard-hitting hammer that is required to force the titanium firing pin into the primer hard enough to fire the weapon. That hammer doesn’t touch the free-floating firing pin during chambering of a round or when the rifle is dropped. A firing pin spring simply isn’t necessary and is a solution looking for a problem that doesn’t exist.

I have two AR-15s available to me that I have tested. One, a Colt, was manufactured in the mid-1970s and the other is a Sig M-400 manufactured in 2015. Neither rifle will slam fire when chambering a round or when rapid firing. I have to pull the trigger for either rifle to fire. I don’t drop rifles, so I’m willing to accept the findings of others who claim that dropping the rifle will not cause it to slam fire unless it is defective.

One problem that has ben noted is the use of soft primers. The military uses hard primers on their 5.56 ammunition. Those of us who load our own ammunition should stick to CCI #41 primers or the equivalent.

Some have suggested that small O rings be used on the AR-15 firing pin. Once again, it is a solution in search of a problem that does not exist. However, the O rings can jam the firing pin so it is locked in the forward position, which I suppose might cause a slam fire.

A safety precaution that knowledgeable AR-15 owners practice is to not use the same cartridge in the top of the magazine more than a couple of times to chamber a round if the round isn’t fired but is ultimately ejected unfired.

The light firing pin doesn’t have enough energy to normally fire the round but can dimple the primer slightly even though the hammer didn’t touch it during chambering.

To avoid several dimples in the primer of the same unfired cartridge, the cartridge should be set aside for use at the range where it will be fired after carefully closing the bolt carrier instead of letting inertia close it.

In all probability, the light firing pin would never fire the piece, but why not play it safe?

The AR-15 has been around for a long time. Most of the bugs were eliminated before it was ever put on the market. Early malfunctions were traced to ammunition that had some carbon in the powder used to fire the 5.56 rounds. A change to cleaner powder with no carbon solved the problem.

If you have or are planning to purchase an AR-15 and would like a more through description of your rifle with lots of illustrations, the Combat Book Shelf prints a manual called, “AR-15, M-16, and M-16A1, 5.56 MM Rifles.” Desert Publications, Cornville, Arizona, 86325

My copy is pretty old and was purchased at an Army store in College Station, Texas.

Smokey Merkley was raised in Idaho and has been hunting since he was 10 years old. He was a member of the faculty of Texas A&M University for 25 years. There he taught orienteering, marksmanship, self-defense, fencing, scuba diving and boxing. He was among the first DPS-certified Texas Concealed Handgun Instructors. He can be contacted at