View Full Version : Sig misfires

July 25, 1999, 07:54 PM
Does anyone have any clues why a Sig would misfire? My P220 has this problem, it's not the ammo (4 different types and all worked in another 45). It has happend in both single and double action. They usually fire on the 2nd or 3rd trigger pull. Any ideas gang?

keep your options open &
never miss!

July 25, 1999, 09:56 PM
Did you have any trigger work done on the gun? if so it could be that a lighter hammer spring was put in and that would cause your misfires. Let me know.

July 26, 1999, 05:45 AM
No trigger work has been done.

George Stringer
July 26, 1999, 07:07 AM
Steve, inspect the sides of the hammer, mainspring etc for signs of rubbing. If nobody installed a lighter spring then there must be something slowing the hammer's travel. If you find any marks to indicate this, carefully polish the offending area of the frame to get rid of the burr or rough spot. If there are no signs of any interference I'd look next at the firing pin and firing pin hole. The pin could be bent or there could be a ding or burr at the hole that is slowing the pin down. If everything looks good you could just need a new mainspring. George

July 26, 1999, 05:42 PM
George, how do I disassemble the slide to check the firing pin? Where can I buy a full power mainspring?
Thanks, Steve

James K
July 26, 1999, 06:26 PM
Hi, Steve,

Did this just start or has it been going on since you bought the gun? Is the gun new or used? Look at a misfire before you hit it again and see if the firing pin mark is centered.

I am thinking of headspace - either excess when the case can move forward out of firing pin reach, or insufficent headspace which prevents the slide from going fully into battery. But those things don't just happen; they would either be in the gun from the beginning or caused by some parts change.


July 26, 1999, 06:35 PM
It's been ongoing since I bouth the gun new, but it has been getting worse (about every 250-300rds new; about every 75 rds. now). No parts have ever been changed. The firing pin strikes look centered on the primers. What would be the measurment from the chamber shoulder at the barrel to the chamber mouth to check headspace ( I don't have a gage).
Thanks, Steve

4V50 Gary
July 27, 1999, 04:49 AM
When it misfires, does the hammer drop all the way down or is it partially down as when you use the decock lever?

Could also be dirty firing pin or firing pin spring or the firing pin channel. Try cleaning out the firing pin channel. Use an acid brush and Hoppes. Continually wipe down the firing pin and allow the Hoppes to run down into the channel. An easier method is to use a parts washer and direct a stream of solvent down the firing pin.

The slide is held together by two roll pins, one of which has been inserted into the other. An armorer would use a roll pin punch to remove the pins. This allows removal of the slide block from the slide. The firing pin safety comes out next (along with its spring) and then the firing pin and firing pin spring will pop out. The extractor is removed by using a flat screwdriver which is applied (not to the extractor claw) to tab near the back. Sig recommends (for police weapons) that the roll pins are replaced everytime the slide is disassembled. The old roll pins are discarded and new ones (with tension and strength) are inserted. Highly suggest you find an Sig armorer who will disassemble the slide (it's held together by two roll pins) to check and clean it. If your buddy-buddy with the local PD/Sheriff armorer, go ask him/her.

Vigilantibus et non dormientibus jura subveniunt

July 27, 1999, 05:38 AM
Gary, the hammer is falling all the way down. I did find a spot where the hammer strut is rubing the frame (actually had a burr on the frame) I stoned both smooth. I'll try it at the range this weekend. Thanks, guys.

keep your options open &
never miss!

July 28, 1999, 07:26 PM
Before you take apart the slide or the workings of the frame, may I suggest the AGI Armorers Video for the Sig P220. I don't know your comfort level with doing such things, but it made my life A LOT easier watching the video and working along with it. Its not that hard to do, but it sure made me a lot less fearfull that I was going to screw something up.

Also remember that the double roll pin used in the slide is NON-resuable. This was mentioned in the video and by SIG. I called SIG and they sent me a couple sets of the pins free of charge.


July 31, 1999, 10:52 AM
Hard to say without looking at the firearm, but you *have* given enough information to get the good suggestions above. :)

With hammer-fired guns like this, there's also a possibility that the slide is perhaps 1/16-inch back from being fully forward. No safety problem with the SIG if the hammer falls, because the barrel/slide are together and fully locked for something like 3/16 of an inch before unlocking begins.

The problem arises from the "shank" of the hammer contacting the bottom rear corner of the slide on the way down to the firing pin. Sometimes, this rams the slide the rest of the way forward with enough energy left to fire the round. Sometimes there's a light strike.

I suspect this because of the occasional *3rd* hammer fall firings you report. Long cases, high primers, goobered cases, dirty chambers, burrs or sticky spots on the slide/barrel or barrel/takedown lever/camming block, and various slide/frame fit or lube problems can cause this.

You may want to videotape your next shooting session and carefully examine the frames immediately before the next jam. Putting a thin white line across the frame/slide will make it easier to see if the slide was not fully forward just before the offending shot.