AR First Build FTF, help!

[fuegoslow]

I put together my first Stag-15 about a month ago and headed off to burro canyon this past weekend. Using a DPMS lower kit, I followed instructions online to put one together. Everything looked good to go. I purchased a DPMS M4 upper and a desert camo stock (possibly a mistake by way of China). Anyway, I used the buffer and buffer spring that came with the stock and now my Stag FAILED TO FIRE. I tried troubleshooting all aspects but couldn't find why I couldn't send my rounds downrange.

I opened the upper and checked to see that my hammer was falling after the trigger pull, it was. After closing the upper, I pulled on the charging handle and the bolt carried a round into the chamber. Everything looked good,(also made sure the firing pin was good to go).

I'm not sure but I think the cheap buffer and buffer spring is causing the FTF. Already sighted in, a pull of the trigger results in a click and a twwaaanngg. This is why I think the spring might not be at full strength. But then again, isn't the spring used for cycling the rifle and to carry the bolt forward to chamber another round? Any Help? Thoughts

I'm planning on taking it to a gunsmith or contacting Matt over at Turners West Covina.(Don't mean to call you out Matt, but you've always hooked me up with knowledge and all my toys).

[Matt C]

It's not the buffer/spring. Don't waste money on a smith for that though, I or someone else here would be happy to take a look at it for you. Might be able to diagnose it online if you provide some pics.

and a twwaaanngg.

[4 Brigada]

You chamber a round, take the safety off and squeeze the trigger. What happens? If nothing then its not the buffer or spring assy.

[Stormfeather]

It's not the buffer/spring. Don't waste money on a smith for that though, I or someone else here would be happy to take a look at it for you. Might be able to diagnose it online if you provide some pics.

+1 here. Provide pics and lets see what we can do.
As a side note, anyone notice how it didnt take Matt but one day to jump back in the mix and start helping folks! Says alot about you Matt! Some folks would be "gunshy" after what you went thru! Says alot about CHARACTER.

[wildcard]

You chamber a round, take the safety off and squeeze the trigger. What happens? If nothing then its not the buffer or spring assy.

I think that's the case because he checked to see if the hammer was even falling.. so I assume it didn't go bang.

Since he's hearing the "thwang" after he squeezes the trigger, it sounds like the bolt/ carrier might not be fully forward prior to the trigger being squeezed. In that case.. it can potentially be a problem with a VERY weak spring, or a carbine spring being used in a rifle length tube, and/ or the user riding the chargining handle down.

If the hammer is flying down and the firing pin is intact, then things are just not connecting properly (assumes that your cartridges aren't complete duds).

[Lateralus]

+1 here. Provide pics and lets see what we can do.
As a side note, anyone notice how it didnt take Matt but one day to jump back in the mix and start helping folks! Says alot about you Matt! Some folks would be "gunshy" after what you went thru! Says alot about CHARACTER.

I was about to say how great it felt to see BWO posting again, its a wonderful name to see

About the AR, Usually FTF victims fall prey to cheap mags/ammo. Are you sure it is chambering the round all the way? Or at all? Did you function test the lower? Maybe the bolt carrier is riding wierd on the hammer and restricting its movement I think were all a little iffy on what is actually happening....

[stevied]

It's probabally something in your trigger group. Take it apart and put it back together using different instructions and see if that works

[PolishMike]

When chambering the first round make sure you pull back the charging handle hard and let go quickly. The whole motion should be a tenth of a second. Dont ride the charging handle down slowly. This could cause the bolt carrier to stop with the cartridge resting on the extractor or other part of the bolt and not being fully seated.
To test this:
After chambering a round - Take out the rear pin holding the upper and lower together. Slowly slide the charging handle back and look how the round is situated in the bolt.

[ar15barrels]

I have seen this problem before...

It may be bolt bounce caused by a mis-located buffer detent.
Here is the test:
Empty chamber.
Close the bolt via the bolt catch.
You should hear a definite "tink" when the carrier hits the back of the barrel extension.
Now check to see if the carrier is ALL THE WAY against the barrel extension, or if there is maybe a 1/16" (or less) gap there.
If the carrier can be moved front-to-back in the receiver ever so slightly, the lower receiver is at fault and holding the buffer too far to the rear.

I have fixed a couple lowers with this problem by making an oversized buffer detent and milling an oversized hole further forward in the receiver.

[Forever-A-Soldier]

.MIL armorer here. If you can't fix your rifle yourself or with help from the board, and you want to come out Palm Springs/Cathedral City way, I'll check your rifle for free and help you with any fixes.

Based on what you said, the rifle should go "bang" even with the cheap Chi-Com M4 stock assembly. It may be out of battery and thus preventing it from firing as posted above. Is your firing pin making any marks on the primer of the round that chambers when you pull the trigger? I assume you have the bolt carrier group assembled correctly, right?

Keep us posted.

F.A.S. Out

[Matt C]

You chamber a round, take the safety off and squeeze the trigger. What happens? If nothing then its not the buffer or spring assy.

For some reason I feel the need to mention the obvious just in case... Don't try this one at home with a live round.

ETA: Unless you are Iggy. then it's ok.

[4 Brigada]

For some reason I feel the need to mention the obvious just in case... Don't try this one at home with a live round.

If that needs to be brought up, please place the gun on the floor step away from it and call someone that can dispose of it properly. And dont ever touch a gun again until the common sense fairy pays a visit.

[fuegoslow]

Thanks to all for the advice. I've edited my original post to include some pics. As wildcard stated, one of my pics shows the bolt/carrier with a small gap towards the front after closing the bolt with the bolt catch. AR15barrels diagnosed it pretty good, but I'm not quite sure if the gap in the picture is what he asked me to look for. Picture is a bit blurry. If this is the cause for the pin not striking the primer, what suggestions do ya'll have?

[ar15barrels]

Thanks to all for the advice. I've edited my original post to include some pics. As wildcard stated, one of my pics shows the bolt/carrier with a small gap towards the front after closing the bolt with the bolt catch. AR15barrels diagnosed it pretty good, but I'm not quite sure if the gap in the picture is what he asked me to look for. Picture is a bit blurry. If this is the cause for the pin not striking the primer, what suggestions do ya'll have?

With the bolt carrier closed and the hammer cocked, can you slide the carrier front-to-back within the receiver?
You should be able to try to move the carrier through the ejection port.

Check something else...

Starting with an empty weapon, close the bolt, but do not release the trigger.
Push out the takedown pin.
Slightly hinge the gun open maybe 1".
Take a plain piece of paper and put a corner of it in front of the buffer's face.
Close the gun down and re-install the takedown pin.
Attempt to pull the paper out.
It should be trapped and get torn off, leaving a piece between the buffer face and bolt carrier.
If it slides out freely, this confirms my suspicion that the buffer detent hole is wrong.

Next test requires you to go to the range.
Remove the stock and loosen the buffer tube.
Remove the buffer detent and spring.
Re-install the buffer tube and stock.
Re-assemble the gun and shoot it.
If it works fine with no more misfires, you have absolutely proven that the buffer detent location is wrong.

[rebelmark26]

When I built my lower, I had a problem with the hammer spring being in wrong. The hammer would fall when I pulled the trigger, but it was a "weak" fall. When I put the spring in correctly, you could tell the difference in the tension and the hammer fell with authority.