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I have a relativity new AR15 that is pretty basic. Standard Mill-spec upper from KE Arms with a KP15 (polymer) lower.
About 50-100 rounds through it.
It is using a JP enterprise silent captured recoil spring.
Standard OK industries aluminum or Magpul magazines.

The issue is that the bolt is locking back every round. After firing, the bolt locks back and I can hit the bolt release and the bolt will go forward loading the rifle again.
Per a recommendation from KE Arms I changed from a standard weight to an H2 buffer with no change. They thought the bolt was moving too fast causing the issue, but the H2 buffer mad no difference.
I have tried multiple magazines and different ammunition with the same results.

I am looking for recommendations on where to look to troubleshoot this issue. What would cause an AR15 to lock back basically every round on a non-empty magazine.
Is this a gas issue, a buffer issue, or could something be wrong with the bolt?

Open to any/all construction recommendations to try to fix this issue.

Thanks in advance.
 
It's probably your bolt catch. Check this thread for help:


 
Last Edited:
Thanks for the tip. I had seen that thread, but wrote it off because I don't have a BAD lever, but just to be safe I pulled the bolt catch out and the spring was just a tad shorter and smaller than a couple others I had in my spare parts bin (black spring on the left).

I put in a new Geissele Maritime bolt catch I had recently bought from their sale since I had it apart and used one of the spare springs. It feels the same to me, but the proof will be in the putting. I'll get to the range this week and give it a try.

1674450243818.png
 
Thanks for the tip. I had seen that thread, but wrote it off because I don't have a BAD lever, but just to be safe I pulled the bolt catch out and the spring was just a tad shorter and smaller than a couple others I had in my spare parts bin (black spring on the left).

I put in a new Geissele Maritime bolt catch I had recently bought from their sale since I had it apart and used one of the spare springs. It feels the same to me, but the proof will be in the putting. I'll get to the range this week and give it a try.

View attachment 1351089
I think you're on the right track.
Sounds like your original bolt catch might have been out of spec.
The Geissele part will most likely be in spec.
 
I think you're on the right track.
Agreed.

....the spring was just a tad shorter and smaller than a couple others I had in my spare parts bin (black spring on the left).
That would be my first guess. Even if the bolt catch itself is in spec, if the spring pocket is too deep, too tight (restricting free expansion), or the spring or plunger itself is out of spec it may not have the strength to keep the catch forced downward and can allow just enough rise to capture the bolt.

You also want to ensure the catch has free movement within the slot. Especially since it's new there may be some tolerance issues with a rough finish or other than can affect performance. That usually wears in soon enough if you drop a bit of lube and manual manipulation to wear them in a bit. With the finish quality of the geissele that's less likely to be an issue. A bit of fine grit wet dry sandpaper can help smooth out the slot as well. (for future reference).

Since it's happened with every round though, I would guess that's likely not the main culprit and would be suprised if that spring swap doesn't fix you up. If not, I would be checking on free expansion of the spring inside the spring hole or checking depth to make sure it's in spec. Adding a DIY plug of some sort in the bottom of the spring cup might be an option to get it within spec, if needed.
 
Is the lower ambidextrous bolt release? There's an additional spacer needed to fill the gap if so.

If not, does the spring provide any tension to keep the bolt catch where it should be?
 
Is the lower ambidextrous bolt release? There's an additional spacer needed to fill the gap if so.

If not, does the spring provide any tension to keep the bolt catch where it should be?
No just a standard left side release.

Well, I replaced the bolt release lever and the spring, and that seems to have resolved the issue. I got 60 rounds through it tonight without issue.
Thanks to all who replied and pointed me in the right direction!
 

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