Colt Mustang MK IV firing issue - Pistolsmith

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Old 09-04-2012, 11:40 AM   #1
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Join Date: Sep 2012
Location: Arkansas
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Colt Mustang MK IV firing issue

Maybe you guys and gals can help me...I bought a second hand Mustang MK IV series 80 plus 2. It was a little dirty but not a bad little gun and the price was right. Everything checked out OK on inspection but when I fire it nothing happens. The firing pin is free and can be moved easily but I'm wondering if there isn't something missing. I'm no gun expert so I am calling on y'all to set me straight. I don't have a problem sending it to the gunsmith for repair, as I got it cheap.

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Old 09-04-2012, 12:32 PM   #2
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Join Date: Apr 2010
Location: North Carolina
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The release timing for the firing pin is probably late, and the plunger isn't letting the firing pin past it. Unless you're familiar with the inner workings of the Series 80 system...detail strip and reassembly and the way the levers's probably better to take it to somebody.
Old 09-04-2012, 12:36 PM   #3
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Thanks! I feel like it is something simple, except for a simpleton, in which case an expert is better...
Old 09-04-2012, 03:41 PM   #4
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It's not a difficult or complicated fix, so it shouldn't be very expensive.
Old 09-04-2012, 05:20 PM   #5
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Posts: 1,800
I'm not clear on "nothing happens".
Does that mean the hammer doesn't drop, or the action simply doesn't operate, or the round doesn't fire?
In the Mustang, the firing pin lock is under the rear sight.
This system is not like the Series 80 system as used in the Government Model and isn't something that usually gets out of order by being reassembled incorrectly.

If you need a professional to look at it, you can send it in to Colt for the real pros to diagnose and repair it.

Here's a owner's manual that includes a schematic. Possibly this will help figure the problems out.

Here's a better schematic:

Here's some possible troubleshooting info. This is from memory so I may have something wrong:

The Mustang is fairly simple.
When the trigger is pulled the trigger bar presses the sear to release the hammer and at the same time pushes the disconnecter upward.
The disconnecter pushes the firing pin lock upward, unlocking the firing pin so the hammer can drive it forward.

First to check the firing pin lock either remove the slide or lock it back and press the firing pin forward with a punch.
The firing pin should NOT move forward unless the locking plunger is first pressed up into the slide.

Next, per the owner's manual check the ejector to insure it hasn't been damaged by pushing it too far down and reversing it.
If someone did reverse the ejector then rammed a magazine in it could be damaged.

With the slide and grips off, check the action of the trigger, trigger bar, sear, and disconnecter to insure they're operating correctly. DO NOT allow the hammer to drop onto the frame while doing this. Control it with a finger.
When the trigger is pulled FIRST the disconnecter should move upward, THEN the sear should be pressed to release the hammer, allowing it to drop.

Last edited by dfariswheel; 09-04-2012 at 05:45 PM.
Old 09-05-2012, 11:31 AM   #6
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Location: Greene County, Indiana
Posts: 14
make sure the weapon is clear!!!!......first off drop a loose fitting dowel rod down the barrel pull the hammer back and fire it.....if dowel shoots out you have ammo trouble...if not remove the slide and check to see if the firing pin block is stuck up.....the firing pin will not move if it is stuck up......might be rust or carbon makin' it stick....

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