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Posted: 8/4/2011 4:39:19 PM EDT
Hi guys, As you can see from my title I have a pretty serious problem going on. Here's the deal; Took my 20 year old Colt Sporter Lightweight. I hadn't shot it in awhile but it has never done this before. Out of every 20 or 30 round mags it doubled at least one time.

I checked for debris in the fire control group. It was clean as a whistle.

Pulled all of the parts to check for damage. All parts looked good.

Replaced the hammer and trigger springs.

After doing the above, the gun is still doing the occasional double.

I have done the manual test to try and induce the empty rifle to do this but it is working as it should, must have done the manual test 200 times and the disconnector is catching as it should and handing off to the sear as it should.

I've ordered a new Colt made fire control group kit but it is on backorder for at least 30 days.

With everything seeming to work as is should except when live firing I'm stumped. Help!!!!!!!
Link Posted: 8/4/2011 5:04:43 PM EDT
Replace the disconnector spring and see if that helps, but make sure you put it in with the large end in the trigger.  That would be the first thing I would check if it was working when you put it away and then years later, it has suddenly started doubling.  The spring could be broken, rusted in solid, or any number of ailments including having just died of old age.
Link Posted: 8/4/2011 5:30:13 PM EDT
Originally Posted By Big-Bore:
Replace the disconnector spring and see if that helps, but make sure you put it in with the large end in the trigger.  That would be the first thing I would check if it was working when you put it away and then years later, it has suddenly started doubling.  The spring could be broken, rusted in solid, or any number of ailments including having just died of old age.


I looked over the disconnector spring real good and it looked fine, however I did not have a spare so I couldn't replace it. But when I did the manual testing the disconnector snapped into place catching the hammer hook as it should.

Link Posted: 8/5/2011 6:22:42 AM EDT
Hand testing does not always reveal the fly in the soup because things are happening so much quicker when live firing than when hand cycling or function testing.  You might take the FCG out and make sure the trigger pin going through the disconnector is not gummed up and is debris free and lightly oiled, as well as the slot in the trigger where the disconnector sits and the sides of the disconnector itself.  If dried oil is causing the disconnector to move sluggishly it may well pass the function test only to fail during live fire.
Link Posted: 8/5/2011 6:57:42 AM EDT
Try the disco test very slowly. I have seen one fail when the trigger is pulled slow, but pass every time it was done fast.
Link Posted: 8/5/2011 7:48:32 PM EDT
Link Posted: 8/5/2011 8:22:59 PM EDT
Originally Posted By Dano523:
Originally Posted By ar556223:
Try the disco test very slowly. I have seen one fail when the trigger is pulled slow, but pass every time it was done fast.



Try that to see if the release timing of the hammer from the disco is too advance, hence the trigger front sear not in the correct position to catch the hammer when it's released from the disco.  If that is the problem, then either replace the FCG, or being the disco back into tune.


Next try this,

Hold the trigger back, pull the charging handle all the way back, then let the charging handle/B/C fly home while you are still holding the trigger back and no mag in the rifle.  

Now release the trigger, and see if you can pull it again. If the disco is not holding, then the hammer is going to be release when the B/C slams home.  If the disco held the trigger, then hold the trigger back again (tape if if needed, lock the B/C on the bolt catch, then hit the release to allow the B/C to crash home even hard.

In both cases, the disco should have held the hammer as the trigger was retained, and if need, Replacement FCG, or if the parts are still in good shape, new disco spring and re-tune the disco.


I'm working a night shift right now but I'll give this a try in the morning when I get off duty. Have already tried much of this but everything seems to be in good working order. I did order a new colt disconnect spring today from Brownells.

Link Posted: 8/12/2011 12:02:18 PM EDT
Just to give you guys a update. Yesterday I received a new Colt disconnector spring in from Brownell's and installed it. Took the old A2 out and put a little over 100 rounds through it. Problem solved, no more doubling.
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