AR won't fire

tbarile

New member
I put about 10 rounds through my AR (dpms upper/plum crazy lower) and on the 11th shot the firing pin hit the primer but nothing happened, I ejected the shell and tried another with no luck. I pulled the bolt and wiped it down but still no luck. Each primer had a dimple from where the firing pin was striking? I plan on cleaning the bolt really well tonight but do you guys have any other suggestions of what is causing this? Thanks
 
Handloads, factory ammo? Look over the bolt carrier and fp then make sure the springs are all good. Replace with milspec parts.
 
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Originally Posted By: Vent_O_LaterIs your bolt closeing all the way?


This is most likely the trouble, especially if you are shooting reloads.

If the bolt looks like this, or even less exaggerated it will cause a light primer strike.

IMAG0222.jpg
 
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Every primer will have a slight dimple from the fireing pin being free floating. Pull the lower cock the hammer put your finger in front of the hammerso it doesnt hit the lower and see how much force the hammer has. Trigger and hammer springs installed correctly, bolt closing allt he way?? If the bolt isnt closed the hammer cam hit carrier and not contact fireing pin. As long as the fireing pin moves freely, i doubt its the carrier.
 
Check the area down in the trigger group to insure that you don't have a loose primer stopping the full movement of the hammer...Otherwise, it sounds like your bolt isn't closing all the way, but I doubt that the firing pin would be able to reach the primer, if that's the case...
 
Just something else to check if the above suggestions don't solve your problem:

I had something similar happen once and it turned out to be small brass debris inside the channel where the firing pin sits, restricting movement of the firing pin. This was on my AR pistol which is really rough on brass, but the point is debris of some sort can impede the firing pin.

arbolt-brass.jpg
 
I am shooting some cheap factory American eagle 55gr rounds until I get through the first 100 rounds. The bolt did appear to be slightly open but I couldn't get it to close any more so I figured it was good. I use ballistol to clean and the carrier seemed a little "sticky". It was around 15degrees out, would that cause ballistol to gum up and not allow the carrier to fully close?
 
Is the upper new? Did you fully clean the reciever extension chamber etc. as long as everythin is clean the bolt should close. American eagle ammo is decent, doubt thats the problem. If the ballistol is a thicker lube, the cold weather didnt help. I like synthetic motor oil.
 
I say throughly clean bolt carrier and chamber, barrel extension. Use some thinner lube and test it. I always look at the bolt after its charged to make sure its closed. Id b pissed if it went click on a yote.
 
My guess is the bolt is not closing all the way. As stated above you will probably always have a slight dimple in the primer on an unfired round do the the floating firing pin. Take a good look at the carrier when your bolt is closed on an empty chamber, then look at it when you have your problems. You should be able to tell if it is closed all the way. If it is not DO NOT USE THE FORWARD ASSIST!!! It will only make the problem worse, the FA is pretty much useless on todays rifle if you ask me. I would also get a chamber brush and make sure your chamber does not have any debris on it too.
 
I had a new RRA lower when one leg on the hammer spring broke after the first clip. Everbody has had some great ideas to check. Best of luck. Call DPMS today on the phone.
 
Take a good look at the locking lug area. If there is any debris in there, it will not let it lock into battery. Even a little gun powder will stop it. Even if it is not locked in battery you will still show a slight strike on the primer.
 
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I would also check to make sure the gas key is properly aligned and tightened as well as staked. If that key is loose or isn't properly aligned it could hang up while the bolt is going into battery preventing full lock up. I've been told gas key issues are the number one most common cause of AR failures.
 
Like reb said, check in your locking lugs. Shouldnt have any problem on the 11th shot and not the first unless you got some debris in bront of your barrel extension. Break it down and spray it down good with some break cleaner into your chamber. If you have some cleaning stars or a chamber brush you should be golden. I use lucas on my carrier to lube, but its probally trash in you lug area.
 
I had a problem last winter in a tourney with my AR. It was slightly above 0 degrees and had the same thing happen. Asked around and someone suggested to use some K4 on the firinf pin after cleaning, which is rated to -60 degrees. Ive never had a mis-fire since and ive hunted in some extremely cold weather. Just remember to use your lubricant lightly. These AR's dont need much. And especially in sub zero weather.
 
Maybe a dumb ?, but is a .223 chamber or a 5.56 chamber? Had a 223 chamber that would do that if a 5.56 round was loaded? just a thought.
 
Really no difference in chambers, unless you are shooting tracer rounds in a .223 chamber. If the barrel is chromed it's 5.56 99% of the time. I say disassemble the bolt and inspect the firing pin length, or just change the firing pin
 
Have you done a functions check? Does it sound like hammer is slamming the firing pin forward?

Did you call and ask what their recommendation is?
 


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