I'm having a problem with the Mosquito.
It was, not ejecting, it looked dirty so I cleaned it and still fires but won't eject....??

mosquito's are finicky they require higher powered 22LR Like CCI MiniMags, if you run cheaper lower powered ammo it may not move the slide properly and you'll have failures..

A friend brought one to the range once. After struggling with it for about 8 magazines. I told him he had a great gun. He replied with a pretty shocked what? I told him he had a great gun to practice clearing malfunction with. That does not mean that all Mosquito are jammatics.

I'd clean it really good. Lube the crap out it. Then I would run it with some good solid high power rounds like CCI Mini Mags and such. Don't use the bulk pack stuff. Might just need some breaking in. If still bad, I'd call Sig Customer Service.

OK, I'm going to clean it, again, lube it well and get some Mini Mag ammo...tnx

The one I used to have also ran well with Federal Auto Match .22. Bulk packs of something like 320 rounds for a fair price. Used to get it a Sportsman's Warehouse and maybe even Walmart at one point.

I have owned my Mosquito for many years now. They do not like under powdered ammo ESPECIALLY when they are new and tight. Keep it clean and WELL lubed(dripping) and use CCI MiniMag ammo for the first 600 rounds and you will likely see a different handgun performance wise.

My solution; POLISH the chamber. Then sand the paint off of the rails (upper and lower) and polish them. Then LUBE with a grease/ATF mixture (honey/syrup consistency)...

Thereafter keep the chamber clean and run the gun WET... works for me with all ammo.

Do you have the standard Velocity or the high velocity recoil spring installed?

This thread is almost 5 years old!!!

I know , 5 years …
By now , 90% of Mosquitos are in cut up parts located in a landfill

Just to get this out there, try using a trick bullseye shooters have been using for decades. Load the mags and then run a small bead of oil on the bullet of the top round. Do that for each mag and your gun should extract and eject just fine.