Round not firing when using bolt release on AR15

AR/M4 AR Technical Discussion
1

Happy New Year. I have a problem with my AR and hope that someone can help. When I use the bolt release to chamber the round and then press the trigger the trigger clicks like normal, but the firing pin doesn’t strike the primer, no marks on the primer. If I use the charging handle or during firing when the round is chambered by the rifle everything is fine. Does anyone have an idea of what might be happening? it sounds like the bolt doesn’t move all the way in the carrier, so that the firing pin doesn’t go out enough, but what would cause this to happen and only when using bolt release? I have a collapsible/carbine stock on this lower.

Thanks,
Alex.

2

Test it by hitting the forward assist after you release the bolt catch. If it shoots then you know that the bolt isn’t going forward all the way after you release the bolt catch. Then you can move on to further investigation of the problem.

3

Thank you. I’ll try, problem is I don’t go shooting nearly often enough.

4

Some brands of AR’s (Bushmaster and DPMS come to mind) are kind of notorious for having a relatively tight chamber preventing the bolt from going into battery on occasion. Yours might be one of those. What brand is it?

5

The upper is centurion arms with NATO chamber and chrome lined mid-weight barrel.

6

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A few questions:
What ammo are you using? Only one make or different makes?

How many rounds through the gun?
How many since the last cleaning?

Do you keep the Bolt well lubed?

Lastly, what make is the lower? Was it factory assembled?

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7

Did the rifle just start doing this?

unload the rifle, take the upper off of the lower, remove the bolt from the bolt carrier and slowly slide the carrier into the upper with the upper right side up and upside down.

Do you feel any resistance or hear any noise when the carrier is nearly fully inserted into the upper?

8

This may sound odd but double check to ensure that you put the firing pin back in after your last cleaning.

If the pin is there remove it and make sure that there is nothing obstructing the area where the pin goes in the carrier.

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9

How old is the upper and lower? How many rounds? Make sure that you have plenty of lube on the bolt and carrier. Make sure the length of the action spring is a minimum 10 and 1/16 in long.

10

The retaining pin is most likely not installed correctly.
If you installed it before you put the firing pin in…

11

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Didn’t the OP post the gun worked fine if he releases with the CH but it just doesn’t fire when he releases using the Bolt Release?

If it was assembled wrong, the gun would not function at all.

But maybe it’s just me…

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12

You are right he did say that.
Assuming it does fire when manipulating the charging handle the OP has a different problem.

13

This may sound odd but double check to ensure that you put the firing pin back in after your last cleaning.

14

As already noted, the rifle wouldn’t fire at all if this was the case.

15

Thanks guys for the suggestions. The firing pin is there. The lower is double star and was assembled by me using Daniel Defense lower parts kit with spike’s boron nitrite carrier and bolt and hammer. It only doesn’t work when releasing with bolt release/bolt catch. Works fine any other way.

I took the upper off and slid the bolt/carrier by hand and it slides fine, no sounds or obstructions. The upper has around 600 - 700 rounds through it, the lower about 120.

16

Did you check the recoil buffer spring as mentioned above?

17

Those damn spikes NiB bcg’s again! Must be out of spec due to the application of the NiB and therefore getting hung up!:wink: just kidding, had to say it, but…you never know.

18

Something doesn’t add up here. There has got to be something happening here.

Is the lower receiver extension screwed in all the way (correctly) to where it just engages the buffer retainer pin?

Was the upper purchased complete from Centurion and dropped onto the DS lower?

Who makes the buffer and the spring? What type of buffer do you have?

19

Does the bolt slide smoothly in the carrier? What is the free length of the recoil spring? Does the ejector depress smoothly and fully under the bolt face?

20

It seems like it would have to be something with the spring/buffer/tube. Since the carrier appears to work fine when it’s manually worked there doesn’t seem to be an obstruction in the way.

What I’m thinking is the difference between using the charging handle and the bolt release is the carrier is probably farther back when using the CH. That would compress the spring a little farther and add some additional energy compared to the bolt release.

I would agree with Iraqgunz and think the place to start would be the buffer/spring/tube area.