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Posted: 7/29/2012 4:42:40 PM EDT
I just finished a build using a Zombie Defense lower that came with the trigger group.  While trying the rifle out, I have a doubling problem. Not all the time but several times over 50 or so rounds.  Once is too much for me so I changed the trigger group to a new Geissele Super Semi Auto Enhanced Trigger.  Took it out today and after about 20 rounds, it did it again.  The Geissele comes with the disconnector spring already installed.  I read on another post that this could be a possible problem, but with a brand new trigger group with the spring installed, I'm looking at possibly another problem.  Does anyone have any idea why this is still happening?
Link Posted: 7/29/2012 4:47:48 PM EDT
You probably installed your disconnector spring upside down.  Fat end to the bottom.

If that's not it, come back with pics and we'll work through it.

If an all-factory group is doing it, it's become worn or peened much too quickly - send it back, rather than ruin your warranty by filing the foot of the disconnector to increase the overlap.
Link Posted: 7/29/2012 11:03:19 PM EDT
It's a brand new trigger group.  It's the second new group that I've used in this.  
http://img.photobucket.com/albums/v105/atvjunkie660/Firearms/100_0908.jpg
Link Posted: 7/30/2012 4:35:55 AM EDT
Ammo.
Hammer or trigger pin in wrong place.
Firing pin.
Link Posted: 7/30/2012 7:29:44 AM EDT
Disassemble and clean your bolt carrier group to make sure your firing pin isn't sticking causing slam fires.  Your trigger group holes may be out of spec causing poor engagement.  Unless you have a way of checking this, I would send it back.
Link Posted: 7/31/2012 10:49:03 PM EDT
Thanks, I'll let you know what I find
Link Posted: 8/5/2012 9:12:03 AM EDT
I didn't find anything different from the Zombie Defense lower than that of the Bushmaster, Stag, or Rock River.  I checked pin location and they are the same.  I was wondering if the hammer spring might be too strong and might not let the hammer come back and engage the trigger again, instead, letting it follow the bolt back up and causing the doubling.
Link Posted: 8/5/2012 11:19:04 AM EDT
When you function check can you hear the disco click??? With the gun unloaded, dry fire, hold the trigger back and recharge the rifle, let go of the trigger, there should be an audible click as the disco engages. Could be an unintentional bump fire also..
Link Posted: 8/5/2012 3:59:30 PM EDT
How exactly did you check the pin locations?
Link Posted: 8/6/2012 4:50:19 AM EDT
Quoted:
I just finished a build using a Zombie Defense lower that came with the trigger group.  While trying the rifle out, I have a doubling problem. Not all the time but several times over 50 or so rounds.  Once is too much for me so I changed the trigger group to a new Geissele Super Semi Auto Enhanced Trigger.  Took it out today and after about 20 rounds, it did it again.  The Geissele comes with the disconnector spring already installed.  I read on another post that this could be a possible problem, but with a brand new trigger group with the spring installed, I'm looking at possibly another problem.  Does anyone have any idea why this is still happening?


I suggest you call Geissele right way for advice on what might be happening here.  Your ZD lower may be out of spec.  I've been through several triggers with my one and only lower.  When I installed a Jard single stage, I got a really nice 2# letoff, but also got the dreaded doubling.  Not sure if it was the trigger failing to disconnect or just a bumpfire from the very light letoff.  In any event, I gave up on the Jard and switched to a Geissele SSA-E two stage and have been ultra reliable ever since.  If your rifle is still doubling, something else is going on. - CW

Link Posted: 8/6/2012 7:12:53 AM EDT
Why does that SSA-E look different from these pictured in Geisseles link below?  edit-  Ah nevermine. i thought that was the hammer in your pic.

http://geissele.com/supersemi-automaticenhanced.aspx
Link Posted: 8/6/2012 11:16:17 AM EDT
caliper
Link Posted: 8/19/2012 10:22:49 AM EDT
Got a couple new springs from Geissele.  Going to try it out today and see how it works.  I'll let you know how it turns out.
Link Posted: 8/19/2012 1:30:02 PM EDT
Quoted:
caliper


What we going to do??? Measure it????

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