AR disconnector issue

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gspn

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A few weeks ago y'all helped me begin troubleshooting an AR problem.

Today I think I've got it narrowed down to the culprit...the disconnector. Since a picture is worth a thousand words I've attached a link to a video I shot of the problem.

If I hold the trigger back, and push the hammer back...it will stay back but it won't reset to the firing position.

If I move the selector to "safe" it will force the trigger to reset and I can then fire it. If I push down on the back of the disconnector it will reset the hammer. Or if I slap at the trigger a bit, that will force it to reset too. But if I just push the hammer back...it gets stuck almost every time.

Below is the video. Of course the FIRST time I tried to demonstrate it the darned thing worked perfectly!!! :cuss: :D

After the first demonstration though you should get a good feel for the problem. There were no springs rattling around in there so nothing came loose. This is a Stag Arms gun, from the factory, no mods.

https://www.youtube.com/watch?v=hxY4LRzASjs

I lubed the heck out of it and it still sticks. It feels like it takes a bit more force on this gun to manually set the trigger than on other AR's. Any thoughts on what my next step should be?
 
Okay, first thing first... The reason it re-sets with the safety is the safety physically pushed the trigger back to the 'cocked-and-locked' position. Same as if you pushed on the back of the trigger bow. So, your safety works as it should.

Next, disassemble the entire FCG and examine the parts.

1. Are there burrs, dings, dents or other anomalies on either the disconnect sear or hammer notch? If there are, stone them off.

2. Is the disconnect spring in the trigger?

3. Put the trigger pin in the trigger. Does the trigger move freely on the pin?

4. Remove the disconnect spring and put just the disconnect in the trigger with the pin. Does the disconnect move freely relative the the trigger?

5. Now pull it apart and put the disconnect spring back in the trigger. Put the disconnect back in with just the pin. Does the spring push the disconnect all the way forward so the front nose of the disconnect rest on the front portion of the trigger? Does the disconnect move freely? If you push the disconnect back, does it spring back forward?

6. Pull it back apart, put the trigger alone in the lower with the pin. Does the trigger move freely?

7. Now put the trigger and the trigger spring in the lower. Repeat check of #6.

8. Now put in the disconnect the trigger. Repeat checks of #6.

9. Remove the trigger assembly. Put the hammer in the lower without the spring. Check for free movement of the hammer. Put the hammer, hammer spring and trigger pin in the lower (no trigger assembly) and check for free motion.

10. Remove the hammer from the lower. Install just the pin in the hammer, the 'J' spring should retain it. Put the hammer pin in the left side hole of the lower, so the hammer is on the outside. Install the pin in the trigger with the disconnect and spring out side the lower with as much of the pin sticking out the right side. Install the trigger pin in the left side hole of the lower with the trigger outside the lower. Move the trigger and hammer back and forth and check that the sear and disconnect engage the notches in the hammer.

11. Measure the width if the FCG pocket in the lower. The wide pocket should be .690 +/- .005 inch, the narrow pocket should be .500 +/- .005.

12. Install the safety, it should have been removed to facilitate removal of the trigger group. Repeat steps #6 through #8 with the safety installed. Make sure the gap in the safety clears the tail of the trigger and the safety does not hang up on the side of the trigger tail.

13. Check the springs for damage, pre-set or unusual bending.

Somewhere in there you should find your problem.
 
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sounds like friction to me, try polishing the surfaces where the disconnector and the hammer meet
 
OK, just read your earlier post. Since it fired for 2 mags first, this is probably not the issue. Although the symptoms are almost exactly the same as a backwards trigger spring:
- Cock, will not fire. Go to safe, then fire, then pull the trigger and it will fire.
- Sometimes, will fire anyway.
-Press down on the back of the trigger portion and it will reset also.
 
Thanks Lysander. I have a buddy who has the tools and build-experience to do all of that. I'll print off that checklist and put it on the workbench.
 
the problem is almost certainly the spring that pushes the trigger forward. it's either not installed correctly or is not providing sufficient force.

if you repeat what you did in the video and when you let go of the trigger, it stays back, then try gently pushing it forward with your finger. if it requires very little pressure and feels smooth, then it's the spring. if it requires a lot of force and feels gritty or like something is scraping on it, then you could have some other part that is out of spec
 
Just a quick thought... Now that I think about it friend of mine had a similar problem once a while back.

Look to see if the tail of the trigger is hanging up on the safety. If the hole in the trigger is not perfectly square to the longitudinal plane of the trigger the trigger sits in the pocket at an angle and the tail of the trigger is too close to one side of the safety notch and hangs up occasionally. It can be fixed by filing a bevel on the trigger tail, or replacing the trigger (recommend solution).

And, check to make sure the notch in the safety is centered in the .500" pocket.
 
Either a spring power problem (hammer spring too strong or trigger spring too weak), or the mating surface on the hammer and/or disconnector is too aggressively hooked.

I'd try springs first, then disco, then new hammer. Or just skip the entire trial and error process by installing a better trigger, be it a Geisele, Hyperfire, or a drop-in like Timney, POF, etc.
 
If his safety detent is in the wrong place, allowing the the safety to protrude into the FCG pocket, he'll still have the problem....

Best find out what the problem is before you start throwing parts at it....

Once you get it apart the check I outlined will take about 20 minutes...
 
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If the little spring on the left of the photo is installed upside down .... it can cause issues...

mgr_b12.jpg

You can see it is larger at the base then the top.
 
Jackal said:
Swap out the trigger pack. I bet you can find a usgi trigger set for CHEAP.
Click to expand...
That is real bad advice
Having just an M16 hammer and M16 disconnector installed in a semi auto weapon violates BATFE ruling on possessing a machinegun even those two items alone will not allow the weapon to fire full auto.
Having a full auto bolt carrier installed in the same weapon gives them grounds for intent.
Bad bad idea.
 
That is real bad advice
Having just an M16 hammer and M16 disconnector installed in a semi auto weapon violates BATFE ruling on possessing a machinegun even those two items alone will not allow the weapon to fire full auto.
Having a full auto bolt carrier installed in the same weapon gives them grounds for intent.
Bad bad idea.
Click to expand...

Care to cite a source for such a ruling?

The rules on MG possession are pretty straight forward; you either have one, or you don't, and a receiver that accepts all of the full auto parts or modifications to a weapon enabling full auto fire is the deciding factor on what is or isn't. In short, an M16 receiver is a MG, regardless of parts installed. An AR-15 receiver is not a machine gun unless modified to accept M16 auto sear or otherwise altered for FA fire. In the case of lightning links or DIAS, the part is the MG.
 
Clearly when I say "usgi", I mean semi auto parts. Same as saying "milspec", obviously no one suggests using illegal FA parts when they say "milspec" either. No one is inferring the OP break any laws. Stop splitting my hairs, I only have a few left.;)
 
If you know anyone with another AR, I'd try swapping the entire FCG and safety selector between both lowers. If the problem follows the original FCG installed in a new lower then it's the FCG, if the problem persists in the original Stag lower then it might be an out of spec lower.
 
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