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1stTimeBldr

Cannot pull trigger with pistol grip installed

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I am in the final stages of building a JMT 80% AR-10 polymer lower. Milling went ok, and basic parts installation (pivot pin, mag release, bolt stop, trigger) all went ok. When I install the safety selector by itself, everything works normally - drop-in trigger releases on Fire, does not release on Safe. When I install the detents / springs and pistol grip, the trigger no longer releases on Fire. With the grip installed, I can move the safety selector between Safe and Fire easily and I feel the detent engage in both positions. I have tried the following troubleshooting steps:

  1. Install safety selector only: Trigger functions normally

  2. Install safety selector, and grip screw only (no grip or detents ): Trigger functions normally.

  3. Install safety selector, grip, and screw – with the screw backed out several turns (there is about a millimeter of space between the grip edge and the border of the grip mount on the lower. I did this because several posts mentioned that the screw might be overly tight.): Trigger does not function

  4. Install safety selector, grip, and screw fully tightened: Trigger does not function

  5. Take it all apart – Trigger functions normally

 

I am at a loss – I do not know how the grip could be affecting the trigger. Any ideas?

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2 hours ago, 98Z5V said:

Pics will help, here.  Sounds like the grip screw is too long, goes into the lower, and contacts the bottom of the trigger. 

Can't tell without pics, though.

Welcome aboard - go rip up the intro section, and tell us about yourself.  It's right here:

https://forum.308ar.com/forum/22-introductions/

my first thoughts also or 80% saftey holes are off by a thou or two. add a washer in the mix of the grip screw for starters.

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I believe I have found the cause.  When I install the safety selector (before the detents, spring, and grip) and push it all the way through so that the selector lever is flush with the surface of the lower, if functions normally.  During grip installation, I can feel the detent engage and the selector pushes out to about a millimeter above the surface of the lower.  The selector crossbar has a raised lip where it goes into the hole on the other side of the lower - and when that pokes out into the well, that's enough to prevent "Fire" from functioning.  So, I know the cause but not the fix.  Is this just a bad selector?

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5 hours ago, 1stTimeBldr said:

 The selector crossbar has a raised lip where it goes into the hole on the other side of the lower

Sounds like a Battle Arms 45* selector.   Get a pic in here of what you're talking about, on that selector... 

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The selector is a no-name that came with a lower parts kit.  Interestingly, the replacement I ordered is a Battle Arms.  They all have that same lip or rim to fit the hole drilled in the lower.  The problem here seems to be that the detent is pushing it into the well a bit.  I should get the new selector in a few days and hopefully that fixes it.  

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On 12/19/2020 at 1:59 PM, 98Z5V said:

 Get a pic in here of what you're talking about, on that selector... 

 

On 12/19/2020 at 2:51 PM, 1stTimeBldr said:

The selector is a no-name that came with a lower parts kit.  Interestingly, the replacement I ordered is a Battle Arms.  They all have that same lip or rim to fit the hole drilled in the lower.  The problem here seems to be that the detent is pushing it into the well a bit.  I should get the new selector in a few days and hopefully that fixes it.  

Again, Get a pic in here of what you're talking about, on that selector... 

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I'm not sure if I'm tracking here, but what I think is happening is that you've installed the grip and it's grip safety, THEN you're trying to install the Safety...  and it won't go,because the detent is pushing it up out of the way?...

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I think the problem is his safety detent hole is just a bit to much to the center of the lower and is pushing the safety back out of the lower just enough. So the safety doesn't clear the trigger. That's how I understand bthe post. Pics sure would help.

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20 hours ago, shooterrex said:

I think the problem is his safety detent hole is just a bit to much to the center of the lower and is pushing the safety back out of the lower just enough. So the safety doesn't clear the trigger. That's how I understand bthe post. Pics sure would help.

This is probably the issue.  The hole was pre drilled, nothing I can do about that.  I am hoping that the on-order safety is just a little narrower, enabling the trigger to clear the safety.  If not I think I am out of luck.  

lower safety.jpg

lower 1.jpg

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21 hours ago, 98Z5V said:

I'm not sure if I'm tracking here, but what I think is happening is that you've installed the grip and it's grip safety, THEN you're trying to install the Safety...  and it won't go,because the detent is pushing it up out of the way?...

No; the safety gets installed at the same time as the grip and detent.  When the detent engages the safety, it pushes the safety about a millimeter inwards, and that blocks the trigger from acting.  

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6 hours ago, 1stTimeBldr said:

No; the safety gets installed at the same time as the grip and detent.  When the detent engages the safety, it pushes the safety about a millimeter inwards, and that blocks the trigger from acting.  

That's a bad safety, then - not machined right, just like you thought. The actual safety lever shouldn't shift left-right, when you engage it.  If that's happening, you could cut that thing, and make it work. 

Edited by 98Z5V

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My replacement safety selector arrived, and while the overall dimensions were identical, I saw that the well for the detent was cut much narrower.  I installed the selector, detent, pistol grip, etc. - and as the safety detent engaged I felt the selector pop out a bit towards the lever side.  Exact same problem.  The clearance between that and the trigger bar (not sure of the terminology) is so small that this prevents the trigger from firing.  So, it is either a defect in placement of the detent hole (factory drilled) or in my milling of the fire control group pocket.  Although it seems unlikely, I am tending towards the detent hole being misplaced, because on every other AR, the selector switch is flush with the lower - not pushed out about a millimeter (see attached picture).  Either way, I think this lower is a dead issue and I need to start over.  

ar10 safety.jpg

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You could alternatively fix it for free if you have a file. Widen the safety selectors flat section on the side that's engaging the trigger's tail. Should take about 5 minutes at most.  

Pardon the random ambidextrous safety selector image; but either left or right where the purple arrows point. Be careful not to dig into the flat spot in the middle.    

8832a747-5ced-40b8-b8b9-8401413322df.jpg.optimal.jpg

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7 hours ago, Lane said:

You could alternatively fix it for free if you have a file. Widen the safety selectors flat section on the side that's engaging the trigger's tail. Should take about 5 minutes at most.  

Pardon the random ambidextrous safety selector image; but either left or right where the purple arrows point. Be careful not to dig into the flat spot in the middle.    

8832a747-5ced-40b8-b8b9-8401413322df.jpg.optimal.jpg

That right there is the legitimate fix! As long as you don't cut into the flat itself it's a perfectly safe fix, probably take a bout 2 minutes.

Go to the hardware store and buy a 'fine' mill bastard file, grind the teeth off of one edge to make what's called a 'safe edge' and you won't even have to worry about cutting into the flat!

Both of those safeties could be made to work in less time than it takes to go online and order another receiver but hey, it's your money!

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