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 Home shop Mosquito trigger job
pogo  [Member]
8/30/2008 9:53:00 PM EST
Well, I finally dug into my Mosquito after thinking about it for a year or so.

The trigger was rough and gritty, with a loooong pull. I had to fix it or get rid of it.

Looking at the trigger pack inside the frame, it looks like most of the rough pull was due to the cast trigger pack housing rubbing against the trigger bar. I took a stone to the trigger parts and polished them up to get rid of the rough pull.

After taking the trigger pack apart, I could not find the sear. It turns out the sear spring IS the sear, and the part that bears against the hammer IS the sear with its rough edged stamped finish. I stoned that smooth. This had, I'm sure, the most effect on smoothing the trigger pull.

I put it back together, and while the trigger pull is longer than I like, it is tolerable and smooth.

This was a very easy fix. All the stoned surfaces fit inside the plastic grip housing with nothing seen from the outside.

The hardest part is getting the pistol back together. Lots of little parts that are held in place only by fitting the trigger pack in the plastic grip housing.

Take lots of pictures while disassembling it so you don't end up spending a lot of time figuring out where that last spring goes.
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Armin_Tanzarian  [Member]
8/31/2008 4:39:39 PM EST
Great info! Thanks!

I picked one up a month ago to give me some cheap practice with a DA/SA trigger pull. Being 3/4 of the size of the P226 makes it almost identical in size to my P239 so it's a great trainer.

I've been having trouble with my trigger sticking after each shot. It just sticks in the back of the tigger guard and I have to manually push it forward after eash shot. I cleaned and lubed it as best as I could and it still does it. I'd pretty much just decided that I have to send it back.

After taking the assembly apart and having a first hand look at it, do you have any idea what the problem could be? Thanks!

pogo  [Member]
8/31/2008 9:03:19 PM EST
Yeah. It is probably the spring on trigger bar on the right side of the trigger assembly.

It fits into a little hole on the trigger bar and is not very well captured.

Lift up the trigger assembly about 1" out of the grip frame to look at the spring. To do this, remove the slide, then the screw capturing the barrel. Remove the takedown lever screw and pull off the take down lever. Tap out the cross pin holding the trigger in place.

Wiggle up the trigger assembly and watch for the slide stop on the left (very tiny spring) and the trigger bar on the right. One end of the trigger spring fits in a tiny hole on bottom of the trigger bar and the other in the trigger frame.
Armin_Tanzarian  [Member]
9/1/2008 1:37:33 PM EST
Thanks! I'm not much of a 'smith so I'll have a look later tonight and see if it seems like something I want to try. The first time I took my MKIII apart it took me a few days to get it back together. LOL
pogo  [Member]
9/4/2008 9:23:13 PM EST
Don't feel bad. My Ruger Mk 1 was in a coffee can in pieces for ~15 years until last year.

I put ~100 rounds of Winchester Wildcat and Remington High speed through it. I got better groups standing than I used to off the bench due to the far smoother trigger.

It would be a simple matter to reduce the trigger pull weight by grinding at the sides of the sear spring, and reducing the length of pull by working on the hammer.

This pistol could become my favorite .22 pistol.
SeanK1ng  [Member]
9/6/2008 6:25:07 PM EST
I just bought a Sig Mosquito with the threaded bbl as well.

The trigger sucks though I'm not sure what it'll be like until I fire it.

If you get a wild hair Pogo, please feel free to post some pics of what you polished and how you disassembled. I'm not a gunsmith by any stretch of the imagination, but I'm sorta mechanically inclined. With a few pics, I'd give it a try.

Thanks for the notes regardless.

Sean
sdrct  [Member]
9/7/2008 12:37:35 PM EST
Sean- The first step in your trigger job needs to be breaking the pistol in. Conventional wisdom is to start with CCI MiniMags, run it pretty well oiled (especially the little hole that SIG says in the directions to oil), and try some other brands of ammo further downstream. Also pay attention to which spring you are using. SIG really responded to the early problems with Mosquito pistols, and most problems that I have seen posted have gotten resolved with a good break-in. I think of it as the 1,000 round trigger job, and it worked for me (but I want to see some photos too!).
SeanK1ng  [Member]
9/7/2008 2:08:37 PM EST

Originally Posted By sdrct:
Sean- The first step in your trigger job needs to be breaking the pistol in. Conventional wisdom is to start with CCI MiniMags, run it pretty well oiled (especially the little hole that SIG says in the directions to oil), and try some other brands of ammo further downstream. Also pay attention to which spring you are using. SIG really responded to the early problems with Mosquito pistols, and most problems that I have seen posted have gotten resolved with a good break-in. I think of it as the 1,000 round trigger job, and it worked for me (but I want to see some photos too!).


Ya, before I do ANYTHING to the trigger, I've got to make sure it runs reliably. I'm sure if there is a problem and I need warranty work, Sig would frown upon me modifying anything, so I'll make sure it works first, then if I decide I want to improve the trigger, I'll look into polishing the parts.

Thanks for the input though. I just bought 300 rounds of CCI mini-mags to put through it.

Sean
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