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Posted: 2/15/2013 10:54:05 AM EDT
Does anyone know if there is a Mil-spec for the clearence between the hammer and disconnector when the trigger is released and the hammer is fully depressed to the rear?
I have .020 clearance now but am worried that if I get buildup under the trigger the disconnector may start grabbing the hammer again with the trigger released.

Thank you
Link Posted: 2/15/2013 11:36:42 AM EDT
If you are referring to standard parts from a kit, you are more than likely good.
The hammer and connector are very close by design, the disco is suppose
to catch the hammer during normal cycling while in semi-auto mode on the re-cock.

You would be amazed at how much shit can build up in the lower and not effect the safe operation.
More than likely, if build-up gets that bad, it'll stop firing first.

^ all of this assumes you are using within spec parts, and you have NOT tampered with anything.

How are you measuring this gap?

Link Posted: 2/15/2013 11:41:34 AM EDT
[Last Edit: 2/15/2013 11:42:20 AM EDT by Yama_Raja]
Originally Posted By RPM509:
If you are referring to standard parts from a kit, you are more than likely good.
The hammer and connector are very close by design, the disco is suppose
to catch the hammer during normal cycling while in semi-auto mode on the re-cock.

You would be amazed at how much shit can build up in the lower and not effect the safe operation.
More than likely, if build-up gets that bad, it'll stop firing first.

^ all of this assumes you are using within spec parts, and you have NOT tampered with anything.

How are you measuring this gap?



I installed a RRA lower build kit in my lower.

When I push the hammer back it engages the trigger, locks in place and works like its supposed to.
If I push the hammer as far back as it will go it engages the disconnecter and then will not release until I push down on the rear of the disconnector.
This is with the trigger released.

I triple checked that everything was installed properly but the disconnector still held the hammer with the trigger released.

I then removed .035 off the front of the disconnector to time the disconnector giving it .020 clearance which got it working properly

.020 checked with a feeler gauge at the point the hammer and disconnector are the closest.

The disconnector still engages the hammer by over an 1/8 of an each when the trigger is depressed.





Link Posted: 2/15/2013 12:23:38 PM EDT
This explains what I am talking about. I hope this helps someone besides me.

Pay attention to the disconnector timing part about halfway thru.
For me it is about fixing out of spec parts. not modding the FCG

http://www.jprifles.com/v/v_d3.php?v=original_FC_inst2
Link Posted: 2/15/2013 1:34:48 PM EDT
Performing a function check will show if the fire control group is
working as it should.

http://www.ar15.com/content/guides/functionCheck/
Link Posted: 2/15/2013 1:45:03 PM EDT
Originally Posted By RPM509:
Performing a function check will show if the fire control group is
working as it should.

http://www.ar15.com/content/guides/functionCheck/


SEMI
Place the selector on SEMI. Pull the trigger and hold to the rear. The hammer should fall. Continue to hold the trigger to the rear, pull the charging handle to the rear, and release it,
Release the trigger with a slow, smooth motion until the trigger is fully forward. The hammer should not fall. (if working properly the hammer will not fall but you will hear an audible click as the disconnector releases the hammer so it can engage the trigger, which mine didnt do)
Pull the trigger. The hammer should fall. (This is where it didnt because the disconnector didnt let go of the hammer so it could engage the trigger. It would hold onto the hammer just as if the trigger were still pulled)
The only way to get it to release was to push on the rear of the disconnector to get it to release the hammer.
The disconnector would never let the hammer go regardless of trigger position. Removing .035 from the front of the disconnector allowed the clearance for it to function properly.
Link Posted: 2/15/2013 5:42:26 PM EDT
So it is fixed now?

Link Posted: 2/15/2013 6:12:30 PM EDT
Originally Posted By RPM509:
So it is fixed now?



Yes it works now
My continuing concern is if say the rear of the trigger gets debris under it, it would then angle up slightly and cause the disconnector to again stay engaged with the hammer when the trigger is released.
When it was hanging up it was like only by a few thousandths. But still enough to have to remover the upper to push down the disconnector and get it to release.

This is why I want to see if there is an actual Mil-spec for hammer - disconnector clearance with a fully released trigger.

Thanks
Link Posted: 2/15/2013 7:33:15 PM EDT
Originally Posted By Yama_Raja:
Originally Posted By RPM509:
So it is fixed now?



Yes it works now
My continuing concern is if say the rear of the trigger gets debris under it, it would then angle up slightly and cause the disconnector to again stay engaged with the hammer when the trigger is released.
When it was hanging up it was like only by a few thousandths. But still enough to have to remover the upper to push down the disconnector and get it to release.

This is why I want to see if there is an actual Mil-spec for hammer - disconnector clearance with a fully released trigger.

Thanks


If you are concerned about the AR trigger design getting fouled, then keep your gun cleaner. That's the way it works in combat. The design is what it is. As long as your rifle passes the function check its GTG. It sounds like you have already corrected an out of spec disco timing problem.
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