AR Firing Issue

I was at the range earlier and was using one of my rarely used AR pistols. It is an aero precision lower. As I was shooting, it works for the most part but occasionally I would go to pull the trigger and here that dreaded “click” sound. I have to cycle the charging handle and eject the round, cycling the next round in the magazine. It will continue to work for another spontaneous amount of rounds before it does it again. In a 30 round mag, it will do it anywhere from 2-5 times. Upon inspection of the ejected rounds, I find they are whole. However, there is a small indent in the primer showing that the firing pin struck the primer but was not able to puncture far enough to get it to ignite.

I used the mags and the ammo in other ARs and it all works flawlessly. So I am confident it is the rifle. It is rarely used so I find it hard to believe anything is necessarily broken or damaged. I inspected it and its not even dirty.

My question is does anyone know what the most likely culprit is? I was wondering about the firing pin but another buddy was saying it could be the buffer spring. Any suggestions?

I really appreciate your help.


Take the BCG apart and clean it real good. Only takes a tiny amount of dirt to make the firing pin not hit hard enough.

Check the hammer spring, make sure nothings restricting the movement of the hammer.

Check the bolt face, make sure it’s not dirty.

Check the head space


I had the same problem with an AR. The firing pin was just a tad short. Changed firing pins and no more problems.


Check by stripping and make sure BCG is good and clean as @Tactical_Reviews says. Given what info you have given, make sure hammer spring is installed correctly it will still work when in wrong but wear out faster, if it is in wrong replace it with a new one and install correctly. If that checks out look into a stronger hammer spring. Remember do 1 process then function test so you know what fixed it or didn’t work.


lightly file the shoulder of the firing pin so it extends further, has worked for me :blush:


Could it be bolt bounce?

You said it’s an Aero lower, is it your build? Perhaps it’s buffer weight and buffer spring tension playing tricks?


First guess from me would be hammer spring, swap it for a new one. Shoot me a PM if you need an extra stout one.
Second would be cleaning the firing pin channel.
Third check the dimensions of the firing pin, swap with a known to function pin.
Third, check headspace if not previously done.