Ok, so I am no expert by any means so I figured I would ask you guys. Me and a buddy went out last weekend to sight in my new AR and his as well, while doing so we noticed his was misfiring intermittently, he was blaming the ammo, so I took the exact ammo that would not fire in his and put it in mine, everyone fired no problem, not sure how old his ar is but i was thinking maybe he needs a new firing pin? or can that be adjusted? I did recommend that he take it to a gun smith and to not do it himself. Any thoughts? Thanks.

Firing pin, light hammer spring, or tight chamber could cause it. What did the primers look like?

Is it a factory gun or a built gun? If it is a factory gun has he taken out the fire control group? Make sure the hammer and trigger springs are in correctly. I just went through this with a friend. My buddy asked me to build him an AR and instead of watching he wanted to build it. So I let him and just told him what to do. I guess I was playing on my phone or zoned out when he put the hammer spring in, but sure enough he put it upside down and had the exact same problem. Would fire a couple times then misfire with light strikes on the primer. Told him to send me a pic of the inside of the lower and knew right off the bat what he had did. Told him to take it out and flip the hammer spring. He did and hasn't misfired since.

The primer had a small ding in it. Looked just like mine when loading it in the chamber. After the misfire it still looked the same. As for factory or custom , i believe custom. Ho bought it from a friend used. And i believe his friend built it. Thanks for the replies guys.

Easy enough for you both to pull the uppers and compare the FCG and pull BCG and compare firing pins.

WHAT AMMO? TULA?

the ammo wasnt tula, it was federal 55gr fmj 223, I heard bad things about tula.

It is possible for the cartridges to not be completely chambered. The trigger will still release the hammer and the firing pin might or might not tap the primer. I'd be careful about it, don't want a cartridge to actually fire with the weapon out of battery.

Swap bolts and see what happens.

He may have use JP trigger and hammer springs without a JP hammer -- I've seen that before. You need to use a full power hammer spring on a standard trigger assembly.

I use JP trigger and hammer springs on regular milspec trigger and hammer and have never had a problem. Have ran several hundred rounds through my 5.56 upper and probably a couple of thousand through my 22LR upper.

A couple things about not going fully into battery. Make sure he isn't following the charge handle when he loads it. He needs to either pull it all the back and let it go free or drop from the bolt release. And secondly before taking the trigger apart or replacing parts it might just need a good cleaning.

I'm glad it hasn't given you problems -- are you using yellow/yellow?

It's not a problem for 100% of users/ammo, but it doesn't take long to see that many people running a yellow hammer spring and a milspec hammer have intermittent light strikes. Easiest way to avoid that is to run a yellow trigger and milspec hammer spring. Others grind/cut the spur off the hammer to lighten the mass and up the hammer kinetic energy.

You also have a longer lock time running a yellow hammer spring and milspec hammer.

Yes yellow/yellow. I'll keep that in mind if I ever begin to have problems.