Weird firing pin issue on a MK IV Series 80 - Pistolsmith

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Old 10-05-2012, 07:39 PM   #1
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Join Date: Oct 2012
Location: Kenner, LA
Posts: 1
Weird firing pin issue on a MK IV Series 80

I went to the range the other day and my Colt MK IV Series 80 would not fire. When I got home I took it apart and pulled the firing pin (took some doing as the pin was fairly stuck in the firing pin stop). So once I get the firing pin out I notice that the end that sits in the stop isn't round and has kind of flatted a little so rather than the end looking like this | | it was more like this \ / (not quite so badly but enough that it was sticking in the stop). I have no idea what would have caused this and was hoping someone would be able to help point me in the right direction. I took maybe .002 off the widest part of the flare and now it seems fine but I still would like to know what caused the problem in the first place.
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Old 10-05-2012, 08:01 PM   #2
Join Date: May 2009
Posts: 67
It may be that the firing pin plunger was not clearing the firing pin before the hammer struck the end of the pin, thus deforming the end of the pin.

Remove the firing pin plunger and firing pin plunger spring from the slide and carefully examine them for damage.


Old 10-06-2012, 01:11 PM   #3
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Join Date: May 2011
Location: Florida
Posts: 131
If you are using the "adjustable" trigger and have the overtravel too tight, then the firing pin plunger assembly is not moving the plunger up enough.

That is the draw back of using the adjustable trigger.

The Series-80 is designed to be used without the adjustable trigger to give the levers full swing (I know, some do include the adjustable trigger as a selling point.)

Remove the set screw from the trigger and chances are good that it will not happen again.

Now to fix the parts. Remove the nicks that the firing pin put on the plunger or get a new one.
Old 10-06-2012, 05:18 PM   #4
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Join Date: Jun 2001
Posts: 1,801
As above, if the Colt Series 80 pistol with the firing pin lock assembly is not assembled correctly, is used with an adjustable trigger that's not adjusted correctly, or if the parts are defective, the gun can't fire because the firing pin is locked and can't move.

Since you attempted to fire it enough that the head of the firing pin is deformed, you'll almost have to replace the firing pin and the firing pin lock plunger.
If the system isn't working correctly the firing pin and lock plunger get damaged and must be replaced.

Here's a good schematic on the Brownell's site:

Schematic for ColtŪ 1911 Government Models - World's Largest Supplier of Firearm Accessories, Gun Parts and Gunsmithing Tools - BROWNELLS

In the frame are two levers, parts number 31 and 52.
51 fits on the sear pin, 31 fits on the hammer pin.
These two lever must be installed in the frame correctly so they interlock the right way.
When the trigger is pulled lever 31 must rise up out of the frame to push the firing pin lock plunger up.
It's a common error to fail to get the parts installed correctly and they don't operate properly.

In the slide is the firing pin lock plunger and spring, parts number 10 and 32.
You'll almost certainly need to replace the plunger and the firing pin since they're almost sure to be deformed.

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