Failure to fire issues

[Longshot38]

Alright so my DPMS is having issues that are strange to say the least. On the last couple of outings I have had issues the rifle failing to fire. I will squeeze the trigger, hear the hammer fall, but no bang. Some times I will see an indentation from the firing pin on the primer sometimes I will not and the failure is not regularly repeatable. I took the BCG apart and cleaned everything with brake cleaner and I'm hoping this is a simple fix for this but I want know until the next time I take it out. Any other ideas. BTW the rifles configuration is:

DPMS upper and lower
Mil spec trigger w/ JP springs
DPMS BCG
DPMS barrel w/ rifle length gas system & adjustable gas block

 

[MD2Colo]

Re: Failure to fire issues

Soft striking that isn't regularly repeatable...
Possible trigger springs??

Cheap and easy to replace...

As long as the firing pin is fully seated into the BCG when you reassembled it (not trying to insult your intelligence, seen it happen with army guys on M110s) and the pin doesn't have any carbon buildup on it (which it shouldn't, since you cleaned it) you might be able to rule the BCG out.

I'm also assuming that you have intermittent FTF with different types of ammo, not just one.

Someone else might be able to help more.

just my $.02

 

[Badshot308]

Re: Failure to fire issues

Try putting your stock hammer spring back in. I had trouble with the hammer spring in a JARD trigger installed in an Armalite AR10. It was fine with commercial ammo, but with surplus ammo using Berdan primers, I would get multiple misfires. When I put the stock Armalite hammer spring back, the problem was solved.

 

[Longshot38]

Re: Failure to fire issues

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MD2Colo</div><div class="ubbcode-body">Soft striking that isn't regularly repeatable...
Possible trigger springs??

Cheap and easy to replace...

As long as the firing pin is fully seated into the BCG when you reassembled it (not trying to insult your intelligence, seen it happen with army guys on M110s) and the pin doesn't have any carbon buildup on it (which it shouldn't, since you cleaned it) you might be able to rule the BCG out.

I'm also assuming that you have intermittent FTF with different types of ammo, not just one.

Someone else might be able to help more.

just my $.02 </div></div>

MD2Colo thank you for the input. The only ammo I've run is my own. I haven't purchased commercial ammunition in years and have no plans to start now. But your right at this point if the problem persist I'd say the BCG can be ruled out. The trigger spings are the only other thing that comes to mind. Which is an easy fix seeing as I was wanting to change the trigger out anyway.

 

[Mike_in_FL]

Re: Failure to fire issues

May I ask how old the rifle is or how many rounds through it? Since you reload, what kind of primers are you using? I'm just curious to see if you're using the hardened primers or just a normal large rifle. Oh, and a dumb question, tip of the firing pin isn't broken?

 

[Longshot38]

Re: Failure to fire issues

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: fngmike</div><div class="ubbcode-body">May I ask how old the rifle is or how many rounds through it? Since you reload, what kind of primers are you using? I'm just curious to see if you're using the hardened primers or just a normal large rifle. Oh, and a dumb question, tip of the firing pin isn't broken? </div></div>

The rifle is pretty much new. I just finished it up this year and I have about 3-400 rounds down the tube. I'm using CCI 7.62 NATO primers. And no the tip of the firing pin is not broken.

 

[Badshot308]

Re: Failure to fire issues

Those are the harder primers. You mentioned JP springs in your initial post. Are you running a JP hammer spring? If so, do yu have a standard spring to swap it out with. Also, check to see if the legs of the hammer spring are resting on top of the trigger pin and not underneath it.

 

[Awesymoto]

Re: Failure to fire issues

If your using JP springs then try other ones. I've had light strikes using HORNADY TAP and misfires in the past

 

[Captain Moroni]

Re: Failure to fire issues

Check and make sure the hammer spring isn't on backwards. It can be installed two different ways and one way only gives it about half the power it needs. I have seen these results with a backwards hammer spring.

 

[lazy21]

Re: Failure to fire issues

your problem is your die not your rifle, reason it doesn't go bang is because the bolt has not closed all the way. Check your dies, I'm sure that will solve your problem.

 

[Longshot38]

Re: Failure to fire issues

Lazy I just got a small base die. I'm going to pull all the old ammunition and see what happens next outing also.

 

[Greg Langelius *]

Re: Failure to fire issues

If you don't have a case guage, it's a good investment. An FTF that looks like a light hit could be excess headspace, caused by bumping the shoulder further than intended. If this is also combined with iffy extraction, or outright FTE, excess headspace rises high on the list of suspected culprits. Running factory ammo successfully could confirm such a diagnosis.

 

[oubeta]

Re: Failure to fire issues

I had the same issue on my M16 M4. One of the trigger spring legs was broke off and I was down to one. Replace the trigger spring and you should be GTG. Then check the firing pin.

 

[Longshot38]

Re: Failure to fire issues

Greg I have a both go/no go gauges and tooling to measure the shoulders of the case. I know the issue is not headspace.

oubeta the trigger seems to be my likely culprit. I've been wanting to change it over to a two stage anyway, so that will most likely be upgraded soon.

 

[TenZero]

Re: Failure to fire issues

Mine had the same issue trying to digest milsurp NATO ammo. DPMS CS advised the the .308 chambered guns have two issues with 7.62x51 NATO. First is the slightly more snug chamber,(discussed elswhere) and second, the hammer springs and firing pins in the .308 guns are specifically set up for commercial .308, and will function inconsistently with hard mil-spec primers. (As Badshot mentioned) Their advice: only use commercial factory .308, never milsurp. Problems since: 0.0 The point of all this being, it could definitely be a hard primer issue. I would throw a twelve dollar box of cheap factory ammo at it to find out. Easy.

 

[Greg Langelius *]

Re: Failure to fire issues

Good; I just wanted you to consider the possibility.

I just went through an issue with FTF/FTE this past Friday with a new die setup, and the problem turned out to be excessive shoulder setback.

My case guage identified the problem for me conclusively, and I would have tried it prior to the range outing, except I was 'sure' the shoulders weren't being touched.

Greg