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alvinsmith75

From trigger to buffer spring....

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This is a thread I started in a FB group but figured it would be better suited here.  Looking forward to hear your experiences and feedback.  I will update as i continue testing.

 

So the other day Steven posted about "most" drop in triggers not working in PCC and asking if anyone has welded the bottom of their bcg to help with reset.  Some people have and that has worked.  I have been having issues with drop-in triggers in my PCC and wanted to get to the bottom of "why".  I happen to own a PCC as well as an ar15 so I just finished up some measuring and I believe I have it figured out. 

 

-9mm is a QC10 upper and lower with a NFA standard BCG.  Elftmann AR10 trigger
-AR15 is a Radical Firearms upper, Spikes Tactical lower, with an Aero Precision BCG.  CMC trigger


****side note**** while my CMC trigger functions flawlessly in my AR-15, when I just swapped the uppers, the CMC will not even reset when cycling the bolt manually in the ar9.

 

1. I used a razor blade as a bridge across the bottom of my upper. The razor blade measured .037 thick.
2.  I first measured the 9mm from the razor blade down to the bottom of the BCG that resets the trigger. The measurement was .345 with the blade so .308 without the blade.
3.  Next I did the same thing to the AR-15. The measurement was .300 with the blade so .263 without.

That means the BCG on the AR-15 has .045 more material pushing down on the hammer and resetting the trigger. Someone in the last thread suggested welding the bottom of the BCG approximately .040 thick which would be ideal. Is that the answer to the drop-in trigger problem? The next thing would be which 9mm BCG measure similar to the AR-15 BCG?  Am I going down the right path here to find a solution? I am curious to know what others think.

 

The pic is to help show how i went about taking the measurement.

received_892877347527288.jpeg

Edited by alvinsmith75
spacing

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Comparing bolts I took a measurement on my NFA and my buddies JP from firing pin hole to the bottom.

 The JP bolt measured .009" longer than my NFA

My NFA bolt will not reset a CMC trigger when manually cycled, the JP bolt will.

 

I know they're are certain triggers that will work with all bolts, I'm trying to find which bolts will work with most, if not all triggers.  I believe the measuring method below may be what is needed to figure that.  

 

-My gun functions flawlessly with the milspec fcg.  It has slam fired(hammer followed bolt) once in approx 100 rounds with the Elftmann AR10 trigger and twice with the Elftmann AR15 Match trigger.  The last time I caught a piece of brass to my right forearm resulting in more bleeding than I care to have at a match.

 

-NFA standard bolt measures .290"

-JP bolt measures .299"

20170827_170119.jpg

Edited by alvinsmith75
Added info

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Caveat:  I have 0 experience with PCC. 

 

I have seen this problem in .223 ARs more than one might expect. Tolerance stacking produces strange results. Minor differences in hole location and part dimensions....

 

Conventional wisdom says modify the cheapest part first. 

 

In this case, I would consider adding material to the discimnector to get it to catch the hammer. In many cases that will allow the proper reset. 

 

If that hat doesn't work I would add material to the hammer face to see if it fixes the problem. 

 

If the JP bolt works in your carbine, why not just buy a JP bolt and run it?  (For me, solving the puzzle is a lot of fun)

 

hope you figure it out to put to your satisfaction and thanks for sharing. 

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Have a feeling this is your answer:

 

Pasted the link so as not to take credit from the person who helped me with similar issue.  The fact many of the after market triggers will not work with the ramped style bolt of a PCC has been confirmed many times over for me since this thread and it would absolutely make sense the trigger would work in an AR15 upper and not the AR9 (PCC).  Feel free to do all the technical stuff if that's what floats your boat, but if you are wanting it to run, simply use parts that work and not the ones that don't.  Seems like you're chasing your tail a bit with time could be spent better on the range, being that the answer has already been found.  No?

Edited by Hammer002

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On 9/2/2017 at 6:36 AM, practical_man said:

(For me, solving the puzzle is a lot of fun)

 

hope you figure it out to put to your satisfaction and thanks for sharing. 

Bingo!   We see things a lot alike, so many people have told me well why don't you just go buy this trigger… I don't want to buy another trigger, I love my trigger LOL. I will be buying the Tacoma bolt next week.  Like you said I enjoy figuring out what solving the puzzle. Thanks for all of the input I believe everything you said you would work.

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On 9/2/2017 at 7:27 AM, Hammer002 said:

Have a feeling this is your answer:

 

Pasted the link so as not to take credit from the person who helped me with similar issue.  The fact many of the after market triggers will not work with the ramped style bolt of a PCC has been confirmed many times over for me since this thread and it would absolutely make sense the trigger would work in an AR15 upper and not the AR9 (PCC).  Feel free to do all the technical stuff if that's what floats your boat, but if you are wanting it to run, simply use parts that work and not the ones that don't.  Seems like you're chasing your tail a bit with time could be spent better on the range, being that the answer has already been found.  No?

Thanks for the reply, going to read through it now.

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The "which drop in trigger works with which bolt" issue has been resolved if you buy a Taccom bolt.  The bottom of the bolt is made to the same spec as the AR15 bolt and even though I don't own every drop in trigger to test, there is no reason for it not to work.  

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