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Discussion Starter #1
I’ve got a problem with extremely rare doubling.

The pistol is a Colt Gold Cup series 70 in 45 with a BoMar full-length rib sight. The cartridge is loaded with a 200 grain H&G bullet with 3,7 grains of Bullseye. I’ve had this pistol for over 35 years and it’s been fired over 150,00 times without doubling. Of course, the trigger system has been tuned by a gunsmith several times over its lifetime with me.

The doubling has occurred hundreds of rounds apart. I’ve had two different gunsmiths examine the gun. Two things were changed: sear spring tension was increased a bit and over travel screw was backed out. Disconnector length is in spec. Slide and frame are decently tight.

Is there some other reason, even if very rare besides the obvious disconnector-sear-hammer issues that can cause this to happen?
Am I assuming that a double hundreds of rounds apart ( perhaps 500, 700 or more ) is rare or the start of a more serious issue?

I disassembled the trigger parts, examined them for wear and dirt and I couldn’t find anything that alarmed me. There was some dirt in the channels the trigger slides in. The trigger before cleaning didn’t drop out of its own weight, but it wasn’t tight. After wiping the trigger bow and the frame channels, it would drop out easily.
Can dirt get behind the trigger bow and find its way to the sear-trigger contact and lighten the force sufficiently to cause them to slip on firing? Is this actually possible?

Suggestion and opinions would be welcome!

Thanks

Warren Y
 

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How long since you changed the recoil spring and installed an extra-power firing pin spring?
 

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There have been occassions when trigger manipulation caused doubles. It's something on the order of you pull the trigger, the gun fires, and your finger is only barely tripped the trigger and the gun bounces such that your finger hits the trigger sufficiently again after recoil to fire the gun again. I suppose that is a long way of saying that you are really light pulling the trigger (not that the trigger pull is light) and the gun moves away from your finger, then back to it.

In this sort of situation, a firm pull on the trigger should not produce a double.
 

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I did have a disconnector that appeared in spec but was too short for a particular gun.
Granted, it was not a Colt. Oddball things can happen in guns with high round counts.
 

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By BoMar full length rib do you mean an Elliason style like this?



Does the elevation screw thread into the top of the slide? If so, how far down do you have it set? Is it maybe protruding into the firing pin tunnel and interfering with the firing pin retracting all the way? The reason I ask is that I installed a BoMar BMCS on my Legacy Twin pistols and had that problem. The elevation screw was just long enough that it was protruding enough to catch the firing pin spring and hold it, preventing the firing pin from retracting. I caught the problem during dry fire testing/tuning before I ever put a live round in them. But it may leave the firing pin sticking out enough to intermittently pop the primer.
 
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With an unloaded gun, squeezing the trigger, racking the slide, and still holding the trigger in the fire position in battery, then easing off the trigger, can you hear the disconnector click?
 

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The hammer has to drop after the slide has closed for it to fire. So either the shock of the slide stopping in battery jarred sear loose releasing the hammer, or the jarring has allowed the trigger finger to relax just enough to reset and bounce against the finger and fire, or one more, if the over travel has been backed off too much the bow can slightly push the disconnector back too far lifting the left leaf, or lightening it enough so that the sear releases the hammer when the slide slams shut.

LOG
 
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This vintage of NM should have the old wide steel trigger and the sear depressor spring and small lever ... does your still have all of these parts?

605384
 

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Discussion Starter #10
Here are replies to previous question
605454
Colt GC 45.JPG
s:

Had an 11 pound recoil spring for a couple of months, changed it yesterday to a 12 pounder – seems to work so far!
Firing pin spring is Wolff heavy spring – maybe a year old (possibly 5,000 shots). Firing pin checked for complete freedom and retracts properly.

Happens when my wife is shooting. She’s trying to hold the trigger back until firing cycle is complete, then releases the trigger for the reset.

Had disconnector checked – length was 1.3 – supposedly a good length. Sear and trigger checked OK about 10,000 shots back.
May have them checked again.

Picture of GC 45 BoMar full-length sight. Rear two mounting screws are over the firing pin channel, but the pin moves freely and without any apparent binding.
Have a Colt GC in 38 mid-range with Elliason sight and zero problems.

While unloaded (pistol that is)– held trigger back – racked slide numerous times – releasing trigger you can hear the disconnector pop up into the slide cutout. Have also tried “slapping” the slide with my hand and never had the hammer drop. I’ve heard of people hitting the gun with a rubber mallet, but don’t plan a test like that!

Don’t have the extra GC sear spring. Wasn’t on either GC when I got them. GC in 45 about 40 years ago (over 150,000 shots) and the GC in 38 mid-range over 25 years ago (over 5,000 shots.
Lost my old time gunsmith (to cancer) and he was a stickler for details like springs, dimensions, wear etc. He was only 62 years old – too young to die – and a superb gunsmith – I miss him, his knowledge and advice!!!

Thanks for all your suggestions – I’ll definitely keep them in mind!!

Colt GC 45.JPG
 

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The extra sear spring was used to compensate, I believe, for the heavier steel trigger not returning as fast as a lighter trigger. Perhaps you've had some wear get to a point where the trigger/sear is not quite returning as fast as it needs to.

There are aluminum versions of the wider GCNM available with which negate the original need for the extra sear spring and depressor.
 

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Not a 'smith by any means but I've seen this happen with an obstructed disconnector; debris got in the hole in the frame and would occasionally "hang" the disconnector as it was explained to me by the shop owner and resident gunsmith. It allowed occasional doubles and even a triple once. As I was the rookie at the shop, cleaning the rentals was my responsibility and quick field strips and bore brushes between rentals weren't doing the job. I had to completely disassemble the gun and thoroughly clean it followed by a trip thru the sonic cleaner. That fixed it.
 

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Somethingto keep in mind is the overall length of the disconnector is not the only consideration of that component. From the bottom of the sear pin window to the
1.) the top of disco head;
2.) the bottom edge of the disco;
3.) the top of the paddles.

The relationship and clearances particularly of number 3 and the length of the sear legs must be checked and corrected if needed. It is possible the legs of the sear are not clearing the tops of the disconnector paddles, sear is hanging up then slipping when jarred by the pistol going into battery.

I am not saying this is the problem but I would certainly start there.

Also, from a post it seems like this occurs when the OP’s wife shoots the pistol. Is the length of pull short enough for her?
 
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