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 Post subject: AR-15 Failure to Fire
PostPosted: Tue Dec 29, 2009 7:33 pm 
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Long story short, I built an AR-15, Bolt carrier group is a spikes tactical. Upper was assembled and purchased that way. Trigger springs I think are installed correctly.

I was shooting a box of federal .223 and had 1 round out of about 10 go off, the rest had medium to light primer strikes and all FTF.

This is my first AR, what the hell is going on here?

from the looks of my bolt it doesnt really look like the firing pin protrudes very far when I push it with my finger. Could Spikes Tactical have given me a faulty piece of crap firing pin? What else could it be?

Please help me AR-15 gurus, I have no shame, so if its an F up on my part assembling it I will own it. That being said the lower is a DPMS kit, and I do think that the hammer spring is in fact installed correctly, I could be wrong.

HELP!?

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Last edited by thesupremeking on Wed Dec 30, 2009 10:37 am, edited 1 time in total.

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PostPosted: Tue Dec 29, 2009 7:47 pm 
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Having a light primer strike is generally one of two things; Check to see that the bolt and carrier are properly assembled (IE the firing pin is being retained by the cotter pin, and check to see that there aren't any obstructions in the firing pin raceway, even a small piece of metal shavings or carbon can cause a light strike.) One easy method is to depress the bolt face with one finger and push up on the firing pin with the other hand, there SHOULD be 1/16th" or so of firing pin protrusion.
Pics may help the situation if you can't remedy it yourself.

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PostPosted: Tue Dec 29, 2009 7:48 pm 
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thesupremeking wrote:
Long story short, I built an AR-15, Bolt carrier group is a spikes tactical. Upper was assembled and purchased that way. Trigger springs are installed correctly.

I was shooting a box of federal .223 and had 1 round out of about 10 go off, the rest had medium to light primer strikes and all FTF.

This is my first AR, what the hell is going on here?

from the looks of my bolt it doesnt really look like the firing pin protrudes very far when I push it with my finger. Could Spikes Tactical have given me a faulty piece of crap firing pin? What else could it be?

Please help me AR-15 gurus, I have no shame, so if its an F up on my part assembling it I will own it. That being said the lower is a DPMS kit, and I do know that the hammer spring is in fact installed correctly.

HELP!?


Most likely culprits

1. Did you install the hammer spring correctly? Take apart and look closely. The loop in the spring should be pointing backwards

2. Did you install the disconnector spring correctly? The disconnector spring has a fat end on it. The fat end goes INto the trigger, a lot of people install it wrong.

I don't think your firing pin is at fault, i'm thinking install of the LPK is wrong.


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PostPosted: Tue Dec 29, 2009 7:50 pm 
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double, then triple check your lower assembly. i installed a hammer spring wrong on a build for my friend and had to walk him through fixing my fuck up over the phone while he was at the range. when i initialy did the build i thought i had double checked its right. it wasnt.

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PostPosted: Tue Dec 29, 2009 10:01 pm 
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I just mic'd the pin protrusion on my match AR, came out to be .0285" or .72mm, and I've never had an FTF with this rifle.
The pin itself mic'd at 3.177" +-.0005."
Just letting you know if it might help.

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PostPosted: Tue Dec 29, 2009 10:24 pm 
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remove the upper, cock the trigger in the lower and place your thumb between the hammer and the mag release latch so the hammer does not strike it, pull the trigger, if it hurt then this is working and the problem is in the upper LOL

I wonder if the bolt and chamber are mating well. I would take it to a gunsmith to check out the upper just to be sure.


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PostPosted: Tue Dec 29, 2009 11:40 pm 
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Chadrules, ARs are self headspacing, so I doubt that it's a problem with the bolt mating to the lugs and/or the chamber. But a simple go or no-go gauge would easily tell if there was an issue.

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PostPosted: Wed Dec 30, 2009 10:32 am 
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It looks (to me) like the springs are in right, someone chime in if it doesnt look right. Also I included a pic of the firing pin in its furthest protruding position, it still looks shallow to me.
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PostPosted: Wed Dec 30, 2009 10:36 am 
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does the spring need to come from the top side and down to the bottom side?

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PostPosted: Wed Dec 30, 2009 11:34 am 
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I am at work, so double check this, but it looks to me like your hammer spring is in wrong. The legs should lay flat against the trigger retaining pin. I believe the best fix is to pull the hammer assembly, turn your hammer spring 180 degrees (the loop should be on the back of the hammer with the front of the legs towards the face of the hammer), and then reinstall with the legs of the spring on top of the trigger retaining pin (it should take a little muscle to get it there). This should fix your problem that is now being cause by the hammer not being driven hard enough by the hammer spring.

There is a great BIY guide on AR15.com, and you may want to look at their 15-min trigger job also if you have a DPMS kit. I have two lowers built with DPMS parts and the one that I did the 15-min trigger job to is MUCH smoother. YMMV

*Edit* Your firing pin looks fine to me, and I have never had a bad Spike's product. I am 99% sure it is in your spring.

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Last edited by Snakedriver on Wed Dec 30, 2009 11:37 am, edited 1 time in total.

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PostPosted: Wed Dec 30, 2009 11:36 am 
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OHMR95B wrote:
I am at work, so double check this, but it looks to me like your hammer spring is in wrong. The legs should lay flat against the trigger retaining pin. I believe the best fix is to pull the hammer assembly, turn your hammer spring 180 degrees (the loop should be on the back of the hammer with the front of the legs towards the face of the hammer), and then reinstall with the legs of the spring on top of the trigger retaining pin (it should take a little muscle to get it there). This should fix your problem that is now being cause by the hammer not being driven hard enough by the hammer spring.

There is a great BIY guide on AR15.com, and you may want to look at their 15-min trigger job also if you have a DPMS kit. I have two lowers built with DPMS parts and the one that I did the 15-min trigger job to is MUCH smoother. YMMV


You beat me to it! :lol:

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PostPosted: Wed Dec 30, 2009 12:39 pm 
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yup, hammer springs wrong. the legs should be horizontal across the pin, not coming in at an angle

http://shanedaughtry.com/images/Fire%20 ... mation.gif

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PostPosted: Wed Dec 30, 2009 12:49 pm 
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OHMR95B wrote:
I am at work, so double check this, but it looks to me like your hammer spring is in wrong. The legs should lay flat against the trigger retaining pin. I believe the best fix is to pull the hammer assembly, turn your hammer spring 180 degrees (the loop should be on the back of the hammer with the front of the legs towards the face of the hammer), and then reinstall with the legs of the spring on top of the trigger retaining pin (it should take a little muscle to get it there). This should fix your problem that is now being cause by the hammer not being driven hard enough by the hammer spring.

There is a great BIY guide on AR15.com, and you may want to look at their 15-min trigger job also if you have a DPMS kit. I have two lowers built with DPMS parts and the one that I did the 15-min trigger job to is MUCH smoother. YMMV

*Edit* Your firing pin looks fine to me, and I have never had a bad Spike's product. I am 99% sure it is in your spring.



AWESOME! you guys are all awesome, this fixed it, the hammer spring "worked" but was in wrong. Fixed it and the hammer slams down much harder thanks!

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