Got my new AR, already having trouble.

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Whitman31

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Just got back from the range with my new AR-15, with mixed feelings. The first round in the gun didn't fire, the primer was dimpled, but not significantly. Second round fired, third fired then didn't extract from the chamber.

I ended up having many rounds not fire, and a number of rounds not extracting. I took apart the bolt and cleaned off the "factory" grease, oiled and reassembled. The extraction/jamming problem was fixed, but the gun still failed to fire about 1/3 of the time.

The ammo is new Hornady from Cabela's, not suspecting the rounds.

When an AR firing pin makes contact with the primer, but fails to fire, is that a firing pin problem or a trigger spring issue? The hammer seems to impact hard, making me think the pin is a hair short. Is this common?

My wife is outta town with my digital camera or I'd post pics of the failed rounds as well as pics of rounds that discharged.

I ran most of the rounds that didn't fire back through the gun and most fired eventually. Only a couple never fired.

Could this be a chamber problem?
 
What type of AR15?

That is a unique problem. It's hard to diagnose without being there. Wish I could be of more help. More information would be helpful.
 
I did the lower myself, the barrel and bolt are select match from Shilen, the upper was assembled by a reputable gunsmith...
 
I guess I trust the gunsmith's work because he didn't do much. The barrel came to him chambered and ready to mount. Is there something done when mounting the barrel that could really yield these results?
 
There's not much smithing to putting an upper together. The rifle is headspaced by the barrel extension. It would take a good deal of effort to screw up the headspace or barrel during installation.

That doesn't mean the extension isn't causing too short headspace tho, I've seen it on a couple barrels. I'd have him at least check it for that, since it's his work.

If the barrel is a match one, there's a chance that the chamber is too tight....I've had that problem with a .223 match chamber and my rounds were sticking on feed and extraction.

I ended up having to polish the chamber to get it worked out.
 
I have also heard things such as needing to fire 200 rounds through a gun to sort of break it in. Maybe you havent shot it enough or the AR-15 type is picky about ammo. The varmit hunting AR-15 is ment to take all sorts where as a match grade one can be extremely specific as to what grain and pressure.
 
After thinking about it go with cheap and easy first.

Try different ammo - everyone makes a bad batch occasionally. A box of 20 plinking rounds should cost less than $10 and it might make your day.
 
How about trying a different firing pin in the bolt carrier assembly? Or try another complete bolt carrier. I have parts and a complete one on hand for emergencies. Yes I know you don't want to mix assemblies because of wear but I'm not thinking about match shooting, just making the gun go bang when I need it too.
 
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Are you using a standard AR firing pin or one of the titanium aftermarket firing pins? All stock parts in the lower or any aftermarket parts? Did you clip the hammer spring or any other spring in the lower? Whose bolt carrier group are you using?
 
Not sure I can help. I would probably try another firing pin. I bought my Armalite complete though.

Also, I would try to find military spec ammo. M193 comes to mind. The other number escapes me. Most .223 FMJ you find out there is military spec.

I noticed you mentioned cleaning off the factor grease after shooting. That is a lesson learned for everyone. It pays to pull apart a gun and clean it up out of the box before shooting. I have failed to do that a few times and always regret it. :)
 
OK... Easy now folks

As some one else wisely said, start cheap.
First try different ammo. Most likely, if you are using well made factory ammo this will not be the culprit, but it is worth the $8-$10 to eliminate the easy cause. Next, measure the firing pin. I don’t have the specs with me, but my guess is a quick search of arf.com will get you that info. Next, see if your gunsmith has a go/ no-go head space gauge set and check the head spacing. Also check to see that the bolt is locking up tight and the recoil buffer and spring are not binding and are able to send the bolt home all the way. If all that is good then you may want to look at your trigger group.

Almost forgot. What bolt and carrier are you using?
 
Also, I would try to find military spec ammo. M193 comes to mind. The other number escapes me. Most .223 FMJ you find out there is military spec.
Click to expand...

:confused:
I was under the impression that milspec ammo was 5.56 NATO, and loaded to higher pressures than SAAMI pressure ammo. I.e., the .223 bulk UMC or Federal from Walmart and such is not milspec, but true .223 ammo. This ensures people don't blow up .223 chambered guns with 5.56 ammo.

For more info: www.ammo-oracle.com
 
I am not absolutely certain. I just know that some of the FMJ you find at gun shows or at stores is marked as M193 which I thought was the basic military spec. I guess it could refer to the bullet. I am not sure. I know when I buy cases of brass ammo, I try to make sure they have that.
 
If you have 223 dies, try running the ammo through a full length resizer. Definitely try a go and no-go gauge. Almost sounds like a tight chamber.

Is it chrome lined?
 
Check to see if you have the correct buffer spring and buffer.

Rifle buffer and rifle length spring go in fixed butt stock lowers and carbine buffers and carbine length springs go in carbine sliding stocks.

If you are using an A1 short fixed stock, make sure you don't have it screwed in place with an A2 long upper butt stock screw.
This can prevent the action from fully cycling to the rearmost length of travel which may allow a round to be picked up from the magazine but not allow sufficent force for the action to fully close.

If the action is fully closing during the cycling stage and you have confirmed this with the forward assist, the next step is to check the gas tube and make sure it is properly aligned.
If it isn't properly centered it may be dragging on the carrier key and this may be preventing the bolt from fully seating.

You may have assembled the bolt with the firing pin retainer pin,(the cotter pin), mispositioned.
You may have the cotter pin either in front of, or behind, the fire pin stops on the firing pin.
These are the two raised areas on the firing pin and the retainer pin goes in the space between these two raised areas.
Either mispositioning will cause misfires along with some other issues.

If the firing pin retainer pin is correctly positioned it may be out of tolerance, or bent, and is binding on the firing pin preventing it from completing it's full cycle.

These are a few basic checks.
 
Thanks to everyone (mostly) for all the ideas. I'm kicking myself because at the range yesterday I had another AR with me and didn't swap the pin and/or bolt.

A number of people asked what manufacturer bolt/carrier group came from. At this point I'm not sure about the carrier and firing pin. I know my gunsmith uses a lot of DPMs parts. The bolt is from Shilen, matched to the barrel.

The chamber does not seem too tight, as the rounds that didn't extract fell out when the muzzle was raised up. The bolt always appears to be close all the way. The gas system and buffer all appear to be doing they're job, it leaves a very tight pile of brass.

I haven't mentioned this because I wanted some advice before I got the opinions. The gun is chambered in 204 Ruger. I had 4 boxed of Hornady, 2 from one store, 2 from another, purchased months apart. All 4 boxes showed this problem, I know that doesn't eliminate the possibility that I got a "bad batch" but it makes it very doubtful.

I'm scared that I've to too much headspace, I'm trying to find a go/no go for a 204. I'm hoping it's the firing pin, someone asked if the pin was stock or not, it is. Also the lower parts group is stock, no spring adjustments.

On a good note, when the gun fired the groups were exceptional.

This post was not meant to bad-mouth the AR's design, just looking for some knowledge.
 
Using both 32 and 40gr. ammo, not suspecting this makes a difference because the problem showed up in both "first round" situations after the bolt had cycled a number of times. Thanks though.

This is the same reason I'm not overly concerned about any of the cycling/recoil components.
 
I am not absolutely certain. I just know that some of the FMJ you find at gun shows or at stores is marked as M193 which I thought was the basic military spec. I guess it could refer to the bullet. I am not sure. I know when I buy cases of brass ammo, I try to make sure they have that.
Click to expand...

My bad, I should have been clearer: yes, you can buy 5.56 NATO milspec ammo, but I'd wager that the majority of .223/5.56 floating around is not true 5.56 NATO. M193 is the 55-gr US 5.56 load. M855 is the 62-gr variety which I believe is the current NATO load.

I don't have 4 hours to read through ammo-oracle.com again! :)
 
I had this problem with two of my ARs. Both guns were factory made and both came totally packed with grease. Clean the gun, then clean the gun, then clean the gun again. And I mean every inch of it. If you do not know ARs that well, have a military friend overclean the sucker for you. If you are still having problems, I would suspect a tight chamber or another problem that is not allowing full lock up.
 
This just in...

If excessive headspace was the issue I should see some excessive expansion right? Even in a normal situation you see some expansion. I compared a handful of my empty brass with new rounds and found almost no case length increase, both at the shoulder and the neck. That should rule out an overly large chamber, but the lack of any expansion points towards a tight chamber.

I didn't suspect tight chamber because the shells were not sticking on the way out and the bolt seemed to close completely. In a higher end after-market barrel like Shilen, is it possible I've got a tight chamber but its polished and smooth enough to not see these typical signs of tight chamber.

I'm going to look at the firing pin some more...

Thanks again to everyone who's contributing...

Someone asked earlier if the barrel was chrome lined, its stainless.
 
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