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Suggested solutions to Mosquito Problems

40K views 44 replies 16 participants last post by  Henry88 
#1 · (Edited)
Let me start by saying the Sig Sauer Mosquito has gotten a bad reputation since it came out a few years ago. The problems seem to come from a few different areas. I will try to address them. This should not be considered the only solutions to these problems and not all of them apply to every pistol. These are the most common ones I have found. I'm not an expert. I do own a few Mosquitoes.

Front Sight

The front sight is adjustable by removing one of them and installing a different height sight blade to raise or lower the point of impact. An easy way to remember which one to try next is if it is shooting high put in a higher front sight and if it is shooting low put in a lower front sight. To easily change the front sight. I take off the slide and use a small flat tip screw driver to press one ear of the tabs towards the other ear. I do this through the hole in the slide where the barrel goes through it. Then I wiggle it up and out. The next blade just simply snaps into the slot. The tab only needs to move a little bit. Shoving it hard will result in the tab either being broken or bent to the point where it will not be useable again.

There isn't any fine adjustment so you might have to remove a little material off the top of a higher blade to make it to the right height. It takes very little material removal to make a big difference. I suggest you check the difference between the blades that shoot low and high and then figure what the difference must be. You won't be able to add material so go slow and only a little at a time. You need to be shooting from sand bags or better yet a pistol rest when you are making this adjustment. I just put in a sight that I have to aim a bit low with and compensate by aiming and inch lower then where the bullet will hit. Since this isn't a target pistol it works for me. Another thought is to place the dot of the front sight on the target instead of the top of the front sight blade. It might work in some cases as well. You just need to see what works for you.

Trigger Pivot Pin

The trigger pivot pin can work its way out to one side or the other while shooting the pistol. You can stop this from happening by pressing it out about 1/4'' to the right side and applying a little blue lock tight or other brand medium strength thread locker and then pushing it back into place. Applying the thread locker on the side opposite to the take down lever makes clean up easier. Applying any more then 1/4" of thread locker to the pin will cause problems with the way the trigger pivots. So a little less might be better. Wipe off any excess before it dries. If you are planning to do any work on the trigger I would hold off on this until you are sure you have everything inside done. It will make taking it apart easier for you. Have the hammer de-cocked when trying to move this pin. It will reduce the stress on it and make your job much easier.

The Sport Model

The Sport Model only has a one difference beside the barrel length compared to the standard model. That is the barrel weight. It can be shot with the weight removed and the plug removed in the slide with the front sight blade installed there. You give up some sight radius doing this. The problem with the barrel weight is that sometimes they are hard to remove and put back on again. This is normally caused by the raised area around the indentation on the barrel where the set screw contacts the barrel. This can be fixed by removing the raised area. You can use a fine file or stone to remove the raised area. Only remove as little material as you need to then stop. It doesn't take much to have a barrel weight that is easy to remove and install.

You do need to tighten the barrel weight down good to prevent it from coming loose while shooting. I do wiggle the barrel weight a little when I tighten the set screw to make sure it is centered in the indentation. This makes it easy to get the front sight to align the same each time. If it still comes loose remove the set screw from the weight and apply blue thread locker to the threads and wipe off any excess. Wait for it to fully dry before putting it back in. This will make turning the set screw harder to do and it should not come loose any more. The set screw does need to be turned at least 2 full turns to take the barrel weight off. The amount of torque I use on the set screw isn't measured very scientifically. I snug it up then hold the long end of the allen wrench with a finger and thumb at the very end. I apply enough force to see the allen wench shaft flex just a little. That seems to be plenty for me.

Barrel Screw

The barrel screw is located under the take down lever. This is the only thing that keeps the barrel from wandering. A loose barrel screw will cause jamming and poor grouping when you shoot the pistol. I suggest you apply blue thread locker to the threads of the screw once they have been cleaned. Let the thread locker dry then put it back into the pistol. This was a major problem on the earlier Mosquitoes. It seems the manufacturer has started doing this for later models. The shaft of the barrel screw isn't very thick. If you apply too much torque it is possible to snap it off in the gun or strip it out. It does need to be snug and the barrel assembly should not move up, down or side to side when it is secured.

Like all screws on pistols it is best to use a hollow ground screw driver. The tip of these blades are nearly square in all directions. A normal screw driver has a tapered tip and when looking at it from the side is V shaped. Looking at a hollow ground tip from the side looks like there is little or no V in the shape. Using a standard tip screw driver normally messes the top portion of the slot up or strips it completely. The hollow ground screw driver applies pressure the the bottom of the slot. This is where there is more metal for the driver to apply pressure without damage. You can get these screw drivers at many places such as Brownelles.http://www.brownells.com/aspx/...SMITH SCREWDRIVERSA search for hollow ground screw drivers or gun smith screw drivers should do the trick.

Take Down Lever

The screw for the take down lever can be over tightened. This will cause the lever to be very hard to turn. I have found the reason for this is that over tightening it will bend he aluminum ears of the part (take down lever insert) that keeps the slide guide pin in place. Allowing thread locker (blue) to dry on the threads of the screw before installing will keep this screw from coming loose. I make the final adjustment of this screw when the pistol is completely re-assembled. I only tighten it the minimum to keep the lever from moving while shooting. Since it does have to move 180 degrees to remove the slide the chance of the slide flying off while shooting it with a loose screw is very low unless you are shooting straight down.These are the major areas of concern on the outside of the pistol. The next area is one of the greatest causes in jamming.

The Magazine

Carbon build up in a magazine will cause lots of problems for ammo feeding and the slide not locking to the rear after the last round is fired.
Having your thumb too close to the release lever will also cause the slide not to lock to the rear as well. Also the thumb too close will cause the slide to lock back before the last round is fired.
The Metal Magazines in the Mosquito are probably the greatest cause of this guns problems. The feeder (follower is the name most people would use for this part) does have some problems. I have found several that needed to be sanded down a little to allow them to move easily in the magazine tube. The part that seemed to be the greatest problem was the rounded side. Using some 4 to 6oo grit sand paper and a light pressure quickly removed the excess material.
The next area was the inside of the slot that the feeder axle (guide pin) rides in. I have found several burrs that needed to be removed. The tube seems to be made of rather soft sheet metal (low carbon steel). I used a long flat tipped screw driver to remove worse of the burrs. Then followed this with a little 600 grit sand paper held with forceps. This got rid of the burrs. I have also used Scotch Brite to remove the burrs. It worked pretty good too. Some people have found more burrs on the inside of the ears at the top of the tube. This caused the rim of the bullet case to get caught causing feeding issues. I think running an old case back and forth several times would get rid of these.

I prefer to use dry lubrication in the magazine. I use either dry Teflon (PTFE) or Moly powder. The Moly Powder I use is from KG Coatings on the Internet. I use KG7 and use a Q-tip to apply it. I use the moly powder rubbed onto the sides of the feeder and the feeder axle. I will use either dry lube for the tube and spring. If you use a spray form of dry lube be sure to shake the container before using it. Otherwise you only will be spraying the carrier liquid and not the lubricant.
If you place pressure in the axle from any direction while moving it up and down with the spring removed and feel resistance you still have a problem to be resolved.When installing the magazine spring be sure to have the looped end on the rounded side to the follower. This is the side the bullet portion of the round will be when you load it. It will fit the other way and cause the round to nose dive when you feed a round into the chamber.
If you find the spring twisted when it is removed lay it out until will lay flat on its side before re-installing it.

WARNING WARNING
When removing the spring and base plate on the magazine to disassemble it be careful. The spring is under a lot of pressure. There is a plastic piece (floor plate insert) that will go flying if you do not have your thumb or finger over it when you slide the floor plate off. Release the spring pressure slowly. Do not point the spring plate towards anything breakable or your face. You need this insert to keep the floor plate on and I don't believe you can get just the plate from Sig.

Taking apart the magazine is similar to many other magazines. First you turn it over with the floor plate pointing up. The insert a non-sharply pointed tool such as the threaded end of a cleaning brush or in the field when I didn't have anything else the nose of a non-fired .22 round to depress the plate and slide the floor plate only far enough to not have the tab come back into the hole. Now point the floor plate away from your face and breakable things. Place on thumb over the floor plate and with the other hand slowly slide the floor plate forward. You want your thumb to capture the locking plate and spring when the floor plate is removed. move your thumb slowly straight up from the tube to take tension off the spring. A few pictures might help.







To remove the axle or pin slide the follower down to the bottom of the tube and push the pin out. You can then tip the tube and the follower should fall out. The only place the pin can be removed or inserted is at the larger hole at the bottom of the tube slot.You put them back together in reverse order.

It was pointed out to me that maybe not every Mosquito owner has taken apart magazines before. It is easy to overlook the obvious. There has to be a first time for everything and this thread is more addressed to the beginner then the old pros. My mistake. It is good to have people point these things out to me.This is pretty much the conclusion of the main things to watch out for on a Mosquito.

Ammo

I have found using Federal Auto Match (AM22) and CCI Mini-mags to be the most reliable ammo in the Mosquito. The Federal AM22 ammo needs less force to make it go boom. Anyone having light strike problems should try this ammo. Also placing a drop of oil in the hole on the side of the slide near the safety lever to lubricate the firing pin helps too. The Mosquito needs time to get broken in. These are the two types of ammo I recommend using at least for break in time. That could be as little as a couple hundred rounds or as much as 1,000. After that you might want to try some other ammo to see what works for you. I have found no difference in how the HP and solid Mini-mags function in this gun. You may find that one Mosquito will shoot better with a certain ammo and another one will do better with another. This is true for many rim fire guns. The AM22 and Mini-mags seem to cycle better then most. My Sport Model shoots the best with CCI Pistol Match or CCI SV. CCI Green Tag works about the same as the SV in these short barrels, but the cost difference is a lot. The AM22 are close behind. I do get some light loads with the AM22 that affect the accuracy. They seem to cycle fine and I have had very few duds. The duds are about 1 in every 15 boxes or so. It makes good plinking ammo.

When you are going to try different ammo I suggest using the drop test to see if it is going to give you problems prior to shooting it. The drop test is easy to do. First field strip your pistol. Point the barrel straight down then drop in the round you plan to use. If it seats all the way and tipping it up drops out it probably will work. If it doesn't drop all the way in or come out on its own weight you will probably have problems.

Slide Spring

I use the light spring when shooting ammo that has a fps rating on the box that is less than 1250 fps.
I use the heavy spring for anything over 1250 fps. The Min-mags seem to work well with either spring. If you are having problems with jams and are using ammo rated near 1200 to 1300 fps you might try the other spring to see if they go away.
The light spring is longer then the heavy spring. It has thinner metal for the coils. The light spring is also called the white spring and the heavy spring is also called the black spring. If you look closely you will notice both of these springs have one end slightly smaller then the other end. You need to make sure the tapered end goes on the guide pin and the wider end goes to the slide. Failure to do it this way will cause lots of jams.

I lubricate my guide pin and spring with Moly powder. TW25B or Slide Glide light should work just as well.

Slide Installation problems

If you should have trouble putting the slide back on, you might want to try moving the guide pin for the slide spring until it drops into the hole in the take down block. Often it is at an angle and this will prevent it from going on.
Others have said pressing down on the top of the slide at the front of the ejection port works for them. Also make sure the take down lever is in the proper position.

Lubrication

I have found using Slide Glide light for the rails works pretty good. I have also used Moly powder for the rails and dry Teflon. I found using just oil lasts only for about 50 rounds then it isn't working any more. Depending on the oil used it might not even last that long. The dry Teflon works longer and probably closer to 200 rounds. The Moly powder and the Slide Glide seems to last the longest. Some where near to 500 rounds or more. Make sure you reapply the moly powder, TW25B or slide glide to the rails after every cleaning. There is a rail on the bottom of the slide that the hammer rides when the slide goes back which should also be lubed with the same thing you lubricate the slide rails with. Don't forget to lube the top of the frame ears. They are located on either side of the hammer. When I use the Moly powder I do lubricate everything first with gun oil. Then remove any excess. I then apply the moly power with a Q-tip. Once done I go back and apply the moly one more time to make sure there is enough to get the job done. I also apply Moly to the feed ramp and breech face. It makes cleaning easy and doesn't carbon up very fast either. My wear while using Moly powder is very little. Friction is also very little.
For those not familiar with Moly and want to know more about it try this link: http://en.wikipedia.org/wiki/Molybdenum_disulfideIt is from the popular Wikipedia site. I have found you can apply Moly powder and then add Slide Glide light. It seems to hold up well when shooting a lot of rounds at a time.
Lately I have been trying Slide Glide Light on one pistol and TW-25B on the other. I did apply the Moly powder first before adding the grease. This was for the rails. Both have done well when shooting 500 rounds per pistol. It works far better then any oil I have used to date. I only use Teflon based oil for the trigger assembly (trigger, trigger bar, hammer, sear, Hammer spring. So far it has been the best for these areas. A little goes a long way.
I have come to the conclusion that using Moly powder on the rails followed by Slide Glide light gives me the best lubrication. There is a hole on the right side of the slide just in front of the safety lever. You can apply a single drop of oil in this hole prior to shooting. This will lubricate the firing pin and safety block. Some feel there should not be any oil applied to the firing pin as well.
Here is a link to a video on lubrication: didn't do the video. I just thought it was pretty well done and should be here too.

Bridge Mount (optics mount) Problem with the slide touching the the mount and jamming.

I have had this problem with mine. I believe I caused the problem to start with by tightening the mount screws too much once and over compressed the rail. My solution was to take some shim material .0015 to .003" and made a shim for where it attaches to the rail.The idea was to make the rail a little wider. The shim material is so thin I used scissors to cut it to size and then used a plastic tip screw driver used in electronics to form the bends. I just went around the rail. I removed the screws from the mount and spread it a bit wider then centered my shim. Once it was in the right place I just pushed the screws through the shim material for the rail holes. It was a cheap and easy fix for me. I had everything I needed on hand.
Now when I put the mount on I check to make sure the slide will move freely before shooting. The shim is still used and It even kept its shape pretty well. It might not be what a professional would do. You don't even see the shim when you shoot it. I made my shim slightly smaller then the mount where it attaches to the rail. The shim starts just above the v slot in the rail and wraps down under the rail and back up the other side and ends just above the other v slot.

Note

The take down lever must be turned 180 degrees and parallel with the barrel to allow you to remove or install the slide. Any other position and it probably won't allow the slide to come off or go on.

Many of these problems and suggested solutions were for the earlier Mosquitoes. Some may apply to even the current ones.

Heavy gritty double action

There is a thread dealing with this problem already. I don't plan to re-post it now.
 
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1 5
#2 ·
Hi Dave,

Thank you for reposting this information. I was extremely bummed when it dissapeared from the other website just as I picked up my mosquito from my ffl.

I do have a specific question for you that I was wondering if you could help me with.

Could you send me a pm regarding who you had make the firing pin for you. I contacted Sig Sauer in regards to getting a new one as the the firing pin on my mosquito is neither straight, nor is the rear where the hammer contacts is square.
It really messes with my OCD and I'd like to replace it, but Sig customer service doesn't have them.

Kudos to Sig customer service though for sending me a new rear sight for free.
By the way, there was a spring with the new rear sight that I cant find in the exploded diagram and I couldn't see where it fits. I know it's vague but any clue on this?

Thanks Again,

Sean
 
#3 ·
Gerry is the person that made some extractors and firing pins for me. I have also had him do some nice things for my Sig P6 as well. He has a web site and the turn around time has been pretty fast too.

http://www.totalautomation.us/

There are probably other people out there that might want to get a firing pin or an extractor for the Mosquito and I don't know of any other place to get one.

A PM was sent concerning the spring and the source of these parts.
 
#5 ·
Just want to say, thanks for the info!!

I just purchased a pink Mosquito for my fiance. I disassembled it to give it a clean, and a light lube, but was confused about which springs was the "white" one, and which one was the heavier one, as well as which end (tapered) to slide onto the guide rod.

Had a few jams (at least 1 in every 10) with CCI mini-mags. I had the tapered end of the spring in the wrong direction. Since reading your post, and correcting the spring orientation, it shoots 100% fine now.

I'll try some AM22 as it's way cheaper than Mini-mags.

My fiance and I can now shoot the Mosquito with confidence. Again, thank you for the informative posts on the mosquito!
 
#6 ·
You are quite welcome. Many problems are fairly simple to fix if you happen to know how to do it.

I have shot a lot of the Federal Auto Match in my Mosquitoes. They might not be quite as accurate as the Mini-Mags are, but, they cycle pretty well for me. I don't have any idea how many boxes of them I have shot in a Mosquito. I do know it has been well over 20 boxes of them but probably closer to 30 boxes. I hope they work as well for for you.
 
#7 ·
My son broke his in with 500 mini mags. Since then he has over 2000 Blazers through it without any problems. The only time we did have a problem was when he tried Winchester Super X (I think that's what they were.)

His is a 2010 model I bought him for Christmas. It is far more accurate and shoots better groups than my P22. I don't understand the bad rap these pistols get either. Then again I don't understand the bad rap the P22 gets. Never had a problem with mine and have not done any mods to either one.
 
#8 ·
I read a while back that someone broke there rear sight and had replaced it with a sight that was adjustable for windage and elevation. I cannot locate it and would like to know what sight he used that fit. Filing the top edge off the front sight does not move the white dot. This person claimed that the sight fit and adjusted fine and use a sight from anouther pistol, does anyone remenber this.
 
#14 ·
I've put about a thousand rounds through mine so far and just recently started getting many failure to feeds. I walked through your suggestions on the metal mags but that didn't seem to solve the problem. I've been using a liquid lube (Remington) with teflon on the mags as well but I'll try the dry lube after this weekend.

I had the problems regardless of the ammo used. CCI's or Federal AM22 both had FTF's

Any other suggestions for failure to feeds?

Side note: I purchased it from a gun show and unfortunately it didn't come with another spring.
 
#15 ·
Sig is now selling both the slide springs. They do require a min. purchase of $20 and have free shipping on orders over $100 not including shipping.

http://www.sigsauer.com/SigStore/ShoppingCart.aspx?rcart=update

The difference between the springs is more than enough to cause problems when you use the wrong one. I have worn out a couple of the light springs so far. The rounds start ejecting much too far when it is past time for them to be replaced.
 
#17 ·
The heavy spring is about 3" long and the light spring is about 3.75" long. You could just measure yours with any ruler to see which one you have. I found ammo with a rating under 1250 fps generally works better with the light spring and the heavy spring is needed for anything 1250 and above. I will use the heavy spring with Mini-mags and they have a rating of 1230 fps. Between 1200 and 1250 I tend to try both and use the heavy spring if I don't get miss feeds. I use the the light spring with Federal Auto Match and CCI SV.

I use the light spring more often then I use the heavy spring. It has to do with the ammo I prefer to shoot.
 
#30 ·
Are the 1250 fps ratings determined from a rifle barrel? Twenty three inches or so?

Because a 4-inch LR pistol can hardly shoot at such a velocity.

I shot a friend's Mosquito yesterday and it jammed no-end.

We used hot ammo and standard. Swapped the slide springs. Changed the mag springs to stiffer ones (this worked for a while). Cleaned and relubed with Teflon/PTFE. Loaded ten LRs, instead of 5. Two, six, four. Nothing. The SIG Monquito jammed consistently with everything we loaded it with.

Any suggestions? This is a US$700.00 (Euros 530.00) semi automatic handgun and it's a pity that it works only as a single shot. :eek:
 
#19 · (Edited)
There are a couple of ways I can think of. The first is using a chamber reamer. You can get them at places like

http://www.brownells.com/.aspx/cid=10006/Products/Gunsmith_Tools_-_Supplies

I believe Midway also carries them too.

The second takes more time to do the job. You can use a .22 jag with a 1-1/8" patch and KG Coatings KG 2 Bore Polish. It is an abrasive. I believe the grit is around 1400. That is very fine and won't remove much at a time. You only want to take out the minimum to smooth out the chamber. This might take some time to do it this way. For the inexperiened person, don't run the patch all the way through the bore with the jag. Once or twice probably won't hurt a thing but repeating this often will probably make the gun less accurate. Be sure to clean the chamber and barrel well after using KG2. I would check with the ammo that is giving you problems until it drops in and out by its own weight.

My last suggestion is to try different ammo. The thickness of .22 ammo can vary quite a bit from one manufacture to the next. I tend to use Federal Auto Match in Mosquitoes that seem to have problems. They might not be the most accurate but the price isn't too bad and they seem to feed pretty good. I get them at my local Wal-Mart. You will need the light spring with the Federa Auto Match ammo.
 
#20 ·
chamber polish

Thanks Dave,

Should the patch on a jag be rotated with a drillmotor or just in and out ? I bought a box of Fed Auto Match and 80 of 325 will not chamber witout force applied in 3 of my .22s, is that normal for that ammo? Also the extractor does not reach the case of the cartridge and does not grab the rim as other rimfires do is this normal for a mosqito?

Thank you for your advice.
 
#21 ·
What you are describing is not normal for the Mosquito. I am guessing you bought it new. If so, I do hope you registered it with Sig. If it is new and not registered, you can do that one line. Once registered give customer service a call and tell them the problems you are having feeding and extracting. Also let them know the extractor is not contacting the case. They will probably send you a shipping label and have you send it in for repairs. My guess is the extractor has either a missing spring or a broken spring. They can also check the chamber and make any correction needed. It will then be sent back to you fixed or replaced. If it is replaced it has to be sent to a FFL dealer. If just fixed it can be sent to you. What you are describing should normally be left to Sig to fix. Every so often, any company can let a dud get past them.

Federal Auto Match normally chambers well in most pistols. It is possible with some match grade chambers you might have some problems. I have seen a few chambers so coated with old carbon that nothing would chamber well. With those the only solution was to remove the barrel and soak it in Hoppes’s #9 solvent for a couple of days then use a brush to get it to come loose.

When using the patch on the jag just insert it as far as the rifling and pull it out. Turn it a little and do the same again and again. If you needed more than this the chamber reamer is probably needed to remove more metal at a time. Wolf Target Match seems to drop in most chambers easily. It will also fit most match grade chambers. The cost per round is also quite a bit higher.
 
#22 ·
I believe that I did regester it but it is more than one year old so, out of warranty. I should call them anyway.
The extractor spring is good and will return extractor to it's fully inward position. However the hook part of it does not reach the case and barely snages the rim of a case. With the slide removed and held vertical and a cartridge slid into place the extractor does not contact the case at all and will fall out if tilted.
It seems as if the extraxtor is tool long to grab the front of the rim and the hook is to short to get a full bite on the rim. I hope that I have described the problem.
Thanks for your time and advice
 
#23 · (Edited)
I have had a gunsmith/machinist make extractors and firing pins for me in the past. I'm sure he would do the same for anyone that wants them. I have used both and they work well. I believe the metal used is a bit better grade then the ones the pistol comes with.

http://www.totalautomation.us/

I have done instructions for dis-assembly of the Mosquito. I don't recall If I had pictures for the breach block assembly or not. I do recall writing the steps down. You might try this link and it should be the first post.

http://sigforum.com/eve/forums/a/tpc/f/430601935/m/6730048702

The last post on page 3 has a link for a video someone did about putting the Mosquito back together. I don't recall the video having the breach block having been removed.
 
#26 ·
My quick fix was just swapping ammo to the FEDERAL 375 rd bulk packs, Feeds and funtions EVERY time, even have to use the heavy spring for them. Everything else is kinda hit or miss depending on lot's.

I too did some chamber polishing with a .22 brush covered with a small patch and FLITZ polish, in my drill. Chamber looked like a fluted HK rifle chamber at first, now very smooth.
 
#27 ·
Sent my Mosquito to Sig on Sept.7th, it came back on Sept. 16!!!!!!!!
They inspected pistol, reamed "barrel" and test fired with no malfunctions.
I took it out this morning and fired:

  • 60 rounds of cci mini mag 40gr. with 1 bad primer, no jambs
    60 rounds of remmington "golden bullet" 36gr.HP no jambs
 
#28 ·
was not finished with list so I will start again.

  • 60 rounds of cci 40 gr mini mags[ No failures
    60 rounds of Rem Golden Bullet 36 grHP No failures
    50) rounds of Fed. bulk 36 gr HP with 3 failures to strip a fresh round
    110 rounds of Fed. AUTO MATCH No failures
    40 rounds of 15 year old Winchester HP, 2 fail to feed
    20 rounds of Remington 40gr TARGET /LIST] No failures

    340 rounds with 5 failures from 6 ammo choices!
    I am satisfied with these results.

    I tried some Federal Lightning and they would not cycle , Winchester wildcat would not feed at all!
 
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