Bolt catch failure

[Guest coquiboy]

I purchased a new CMMG complete upper. The bolt catch on my lower does not retain the bolt carrier in the open position. What can I do to resolve the problem?

[Caster]

Do you mean to say, it's not catching the bolt on the last shot? If so there's a handful of reasons for that.

[Guest coquiboy]

I am new to the AR15 family and though that you could open and keep the chamber open by pulling back on the charger and Ingaging the bolt catch.

[Garufa]

You can. Are you pushing in on the bottom of the bolt catch?

[Guest coquiboy]

No I am pulling it out.

[Caster]

Put an empty magazine in the rifle, then pull the charging handle back. Does the bolt catch open then?

[Guest coquiboy]

I installed the empty mag. The the bolt catch works but any small tap on the rifle sends the bolt carrier forward.

[mikegideon]

Spring/buffer under the bolt catch maybe installed wrong? Preventing the catch from moving far enough for full engagement?

[Guest coquiboy]

I will pull it out and see. I may be wrong but I thought there was only one way to install the assembly.

[mikegideon]

Should look like this...

[mikegideon]

I will pull it out and see. I may be wrong but I thought there was only one way to install the assembly.

There is. But there's a remote possibility that something went wrong, like getting springs mixed up. If you get what's in the picture, it could be something else. You also may not be aware, it's possible to break the bolt catch if you drop the hammer on it full force while the gun is disassembled.

[Guest coquiboy]

I took your advice and pulled the catch assembly out. I determined that the catch was not coming up enough to catch the bolt carrier properly. I took the catch and removed a few thousands off the area that meets the spring pin. The catch is now coming up suficently to hold the bolt carrier back. That seemed to do the job. Thanks for pointing me in the right direction. I will be sure to help another brother out in time of need. Thanks a million.

[mikegideon]

What brand was the lower parts kit?

[Guest coquiboy]

The lower parts kit came from Spikes Tactical Model #SLPK101. The complete upper is from CMMG.

[mikegideon]

And the lower receiver? I'm surprised that you had to fit a part. Just trying to figure it out

[Guest coquiboy]

The lower receiver came from LRB Arms.

[mikegideon]

Not familiar with them, but that doesn't mean much

[Guest coquiboy]

This is my first build and I hope to learn a lot more from experienced guys like you. Again thanks a million for your support.

[Capbyrd]

I wish you had taken pics of the spring and pin behind the bolt catch. You shouldn't have had to file anything and its likely that there is still a wrong part in there. Its possible that you mixed up the pins or springs. Its kinda easy to do. Its one of the reasons that I like how CMMG is now shipping their lpk's, they are in color coded bags for different parts.

[Dolomite_supafly]

There should be a plunger on top of the spring. There should be a spring, a plunger on top of the spring, then the catch installed over both of them.

Is it the factory bolt hold open?

The bolt catch should not overpower the empty magazine. If the bolt is going home easily without a magazine in place that is pretty normal.

As far as the bolt hold open and it functioning when actually shooting I think I addressed possible solutions in the other thread.

Dolomite

[Guest coquiboy]

Double checked the plunger and the spring. Both were right. I even tried a new empty magazine before filing the catch.