Gunsmithing New AR15 Fire Control Group Problem?

[kchu02]

Just picked up a complete lower from Rainier Arms yesterday

LRB lower + STAG/CMT LPK.

When I got it back did some dry firing drills to test trigger. I noticed that when I pull the trigger then cycle the bolt to reset trigger that afterwards when I let pressure off trigger, it would fire while I was relieving pressure from the first pull. It would do this everytime.

Is something wrong with the fire control unit? I have a Giessele S3G coming in the mail sometime next week, will this fix the problem?

http://www.youtube.com/watch?v=rD2bo6K6iaE

Gun does something like this, but with every cycle.

Thanks,
Kevin

 

[turbo54]

Re: New AR15 Fire Control Group Problem?

Sounds to me like the disconnector spring and bolt hold open spring are swapped.

In any cae, dont fire it, and/or send it back ASAP. You are in possession of an illegal machinegun.

 

[kchu02]

Re: New AR15 Fire Control Group Problem?

Yeah I'm not going to fire it. It is going straight to my local gunsmith when my Gieselle Trigger comes in on Tues or Wednesday. That will fix it right? I should have them swap the disconnector spring and bolt hold open spring back too right?

 

[kchu02]

Re: New AR15 Fire Control Group Problem?

Could it be a bad trigger or hammer?

 

[gunnergirl81]

Re: New AR15 Fire Control Group Problem?

The disconnector spring could be inverted also. Its slightly wider (looser wrap) at the bottom end that sets into the trigger to help hold it in place, and can wedge in and loose the "springyness" upside down. That would cause the disconnector to not properly engage the hammer and allow the hammer to drop before the sear surface on the trigger is high enough to stop it.

But, generally there has to be something blocking the front of the disconnector to ensure that it fails consistently every time. The disconnector may be out of spec. It is after all just a stamped cut piece of flat steel. We've seen them with the front "arm" deformed and caused the same failure.

The dealer sold you this as a complete assembly? If they installed the LPK they sold you a machine gun. Not intentionally I'm sure, but a defective weapon either way. Its on them to make it right. I can't speak for you but I demand that I get what I pay for, and that it works as it should. I think a call to Ranier is in order.

 

[kchu02]

Re: New AR15 Fire Control Group Problem?

Yeah it was completely assembled. I'll give them a call tomorrow. I might just have local smith fix.it

 

[kchu02]

Re: New AR15 Fire Control Group Problem?

Found my problem. There was a o ring in my fcg

 

[gunnergirl81]

Re: New AR15 Fire Control Group Problem?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: kchu02</div><div class="ubbcode-body">Found my problem. There was a o ring in my fcg </div></div>

Damned O-rings and their shennanigans! Glad you got it figured out.

 

[biner626]

Re: New AR15 Fire Control Group Problem?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: kchu02</div><div class="ubbcode-body">Found my problem. There was a o ring in my fcg </div></div>
You should still call Ranier. Someone dropped an o ring from the BCG in there causing your trigger to fail and they need to know so they can minimize the chances of it happening again.