Sig Mosquito Dis-Assemble and Re-Assemble

Posted April 07, 2010 02:10 PM The old thread is gone and with much help I will try to bring it back more or less. One thought about taking it apart, it may be helpful to have a 1 gallon zip-lock freezer bag to put the pistol in. This may help retain springs that could come loose during dis-assembly. The springs that could give you problems are the trigger bar spring, slide catch spring, hammer spring and the spring in the magazine release lever. Dis-Assembly It is not a hard thing to do if you know how to disassemble and assemble the gun. Let me go through some steps to get here. 1. Unload the gun and remove the magazine. Then field strip it laying the slide a side. 2.Remove the barrel and grips with a good screwdriver. To do this you must first remove the take down lever. There is a screw on the other side. Put the screw into the lever when removed to not confuse it with the barrel screw. Under the place where the lever was there is another screw and this is the barrel screw. Once remove the barrel should slide straight up and out of the frame. 3. Remove the de-cocker spring and lever. 4. Push out the trigger pin. It will help to have it not cocked at this time. 5. Remove the magazine release. Watch out for the spring. It is small and easy to loose. To remove the lever simply push it in with the grips removed. The lever will come out the other side. 6. Pull the action out of the frame from the top. Watch the springs here. 7. Remove the slide release. 8. Remove the trigger action bar and spring. 9. Divide the two half shells of the receiver being careful to capture the mainspring,strut and brass cap. The main spring is under a lot of pressure and will fly out. The 1 gallon bag comes in handy to protect breakable things. 10. The sear is not the spring as someone else has said but a part that fits between the two halves is the true sear. Look at your exploded drawings. 11. Remove the hammer and associated parts. 12. Carefully polish the hammer hooks but don't go too hard on them and keep the angle.

13. Polish the sear face that contacts the hammer. Mine was really rough. Then play with the trigger bar and polish the frame opening that it rides in by the hammer. 14. Pray you have not lost anything and reverse to reassemble. IMPORTANT: Take pictures at each step before and after you remove a part. Study each part on the gun as you go. It will prevent a lot of headaches. Once you do it you know it will be easier if  you have to fix this gun in the future. This is not rocket science and spray rem oil on it after you have it back together. Dave I don't think I left anything out but if you have a problem let me know and I will try to help? I would post a few pictures here but don't know how to on here.I did take a few. My major tool was a fine diamond knife hone from Academy Sporting goods. Wally world used to sell them too. I will sort through and see what I have. Re-assembly The following posts contain instructions on how to put your Mosquito back together. With the half shown in the next picture lay it down on a flat surface as shown

Install spacer on hammer pin

Install hammer and spring. The dog leg goes over the pin and fits in the slot of the spring. These parts are laid out like they will go back into place.

This picture shows the spring and hammer installed. Note the position of the spring. The hammer will be in the cocked position at this time. This reduces the amount of tension on the spring.

Install the other spacer on top of the hammer as shown.

The tapered end of the pin goes through the upper hole of the reset plate. This plate just slides in under the hammer easily. At this time it can wiggle around but should be kept close to the position you see in the pictures.

Ths picture shows the parts in place.

You will now install the hammer spring. The little brass washer goes on the shaft then the spring and followed by the large brass spring retainer. The rounded end of the retainer will be closest to the outside or the point of the shaft. I used a 24 gauge solid copper wire and doubled it up to hold this in place. Since the retainer is rounded it will pop out and go flying before you can get the other half on. Double wrapped around the spring and the half works better then one wrap. Other have used spring clamps. You can leave out the brass washer and this will reduce the double action trigger pull. It will lighten the single action as well to a lesser degree. If you have light strikes put it back in to increase the hammer spring strength.

When the main spring is installed you will need to have the hammer in the de-cocked position and secure the spring to the half you are working on to avoid a main spring flying. Note that I used a piece of 24 gauge solid copper wire to hold the spring in place. I doubled the wire and wrapped it twice around as well.

The next piece to go in is a sear plate. There is a slot where it goes into the half you are working on. The top of the plate should rest against the hammer. There is a grove (Hammer stop) that it should fit into.

This is a close up of the plate properly installed.

This is another view of the plate installed and note the notch on the hammer and the location of  the plate. It will fit in the wrong way and then be quite far away from the hammer.

Place the other half on top at this point. You will need to line it up and it should go one easily. You might have to move the sear plate a little to get it to align with the slot it goes into on the half you are putting on now. The wire is to be remove once you have the halves lined up and there is only a small crack in them where the wire holding the main spring to the original half. You need to make sure the two halves do not separate very much at this point to ensure the main spring doesn't go flying. I just had my wire twisted and the twist was on the out side of the original half. I held the two halves together with one hand and un-twisted the wire with the other. I then used a pair of needle nosed pliers to pull the wire through. I did have two wraps of wire to remove at this time. When the final bit of wire came out through the crack the halves snapped together. I then wrapped the wire around both halves to keep them from separating before I could insert it into the plastic frame.

Turn the halves over to allow you to put in the trigger and the trigger bar. The trigger is put in from the bottom and the halves may need to be separated just a little to get in. There is a pin that will have the trigger bar place on it that needs to go through the slot on the side. Polishing the pin for the trigger bar makes mine have a much smoother double action. This polishing was done be hand and not with any power equipment. It doesn't need much to make it better.

The trigger bar is inserted with the ear going through a slot at the top. It needs to be slightly angled to go in right. Note there is a hole in the bottom of the trigger bar where one end of the trigger bar spring will go.

The other end of the trigger bar spring goes into the hole as shown. I used a needle nosed pliers to get it into the proper place. I did try doing it without tools the first times and scratched the metal up with the end of the spring. While keeping your fingers or thumb on the trigger bar spring, install the halves into the plastic housing. Once the end is in far enough to keep the main spring in place you can remove the wire or what ever else you are using to keep it together from the halves. Only insert it far enough to keep the trigger bar spring in place and maybe just a little of the trigger bar too. You do have to keep the halves together until you get the end into the plastic frame.

Turning it over you will be installing the slide release lever and its spring. I didn't show a picture of installing the spring. There is a post the spring goes on and the other end will be outside of the assembly. I found sometimes you need to keep a little finger or something on the other side of  the spring to prevent it from popping out. Place the release lever on the post as shown and move it up until it hold the spring. Keeping your hand on the lever move the halves into the plastic frame. It should seat all the way down now. You may notice the trigger just flops around at this point and you will have to line it up to go into the slot it should be in.

This is only showing the trigger assembly installed into the plastic frame and nothing more.

There is an alignment tab on the magazine release. You have to keep it in the correct position to get it back in place. Just a little patience and it will go in. Notice the notch in the hole where the magazine release is going to go. There is also a notch on the trigger release as well. You must line these up to get it installed. There is a notch on both sides.

Move the trigger around until you see the hole line up to put the pin for the trigger back in. Once lined up install the pin. If done correctly it should look like this.

These are the parts to put the magazine release back in. I put them in like it came set up for right handed people. You can't set the Mosquito up to release for a left handed shooter. The parts will all fit just fine but the bulge in the magazine to make the magazine safety work will prevent you from being able to insert the magazine. There is a hole on the release for the spring to go into. You will need to insert the round part into the hole paying attention to the notch position. The button you normally would press to release the magazine goes a flush with the frame. Hold it in place and while looking at the other side place the spring in the hole and flat piece with the notched end goes over the spring. Once it is slid into place and then pressed back into the cut out it should stay there by itself. I prefer to install the right grip right after putting in the release lever. I do this so I don't press it out be mistake.

Magazine release in place

The de-cocking lever is in place. Notice how the spring is installed.

This piece of alum. that the slide spring normally rests on is not attached to the take down lever shaft except with friction. You can install it now along with the barrel or after the barrel is installed. Most find it is easier to do it now. You can also put the grips back on as well at this time or prior to installing the barrel. I did not go further since it would be the same procedure you would do to after field stripping the gun. Just remember to re-cock the hammer before putting the slide back on and the take down lever flipped forward. If slide doesn't easily at the first try you might want to have the slide pulled back enough to see the guide pin stick out a bit and just wiggle it a little until it gets straighter. The slide should then go on easily.

The screws for the barrel and the take down lever are the same diameter. The one with the shorter shoulder is the one for the barrel and the longer shoulder is for the take down lever. If  you should try to reverse them the barrel screw will stick out too far for the take down lever to go back into place. I suggest you just place the screw for the take down lever back in to the lever once you have removed it so there won't be any confusion when it is time to put it back together. Putting blue lock tight on the threads of the screws and letting them completely dry before installing them will not let them back out during normal use and make it a little easier to remove them again if needed at some time in the future. The screws need to be free of any dirt, oil or grease prior to applying the lock tight. You can easily over tighten the take down lever screw. This will make turning the lever very hard. Even after you back off the screw. I suggest you tighten it a little and check it. You only want it to stay in place while shooting. The good thing is you are supposed to move it 180 degrees to remove the slide so even if it was a little loose at first you shouldn't have a major problem. Bring your screw driver with you the first time you shoot and tighten it a little at a time until it stays in place. I am seeking suggestions about which pictures should be changed due to lighting angle etc. and

any others that should have been there as well to make it easier for people to get their guns back  together. I have added comments that may help with the pictures above. I'm leaving this part as it was so there isn't too much change all at once. The following is just a repeat of the comments I had put here in the beginning. I left them in for those that may want them. Once the trigger bar is secure, turn the gun over and put in the slide release. Doing it like I did for the pictures is harder to do. The screws for the barrel and the take down lever are the same diameter. The one with the shorter shoulder is the one for the barrel and the longer shoulder is for the take down lever. If  you should try to reverse them the barrel screw will stick out too far for the take down lever to go back into place. I suggest that when you take the take down lever out put the screw for it in the lever so it doesn't get mixed up with the barrel screw. Wrangler suggested putting blue lock-tight on the threads of the screws and letting it dry before putting it back in. This way you will be able to get it back out some day if you ever need to do so. I think that is a very wise suggestion. The amount of material to remove from the sear is only the minimum to remove the black  coating and then a fine polishing. Do Not Change the angle. The ear that the trigger bar mounts on the trigger can be polished and it results in a smoother double action. Using a rotary tool is not recommended for the polishing. You need to move in the direction the contacting parts will be moving against each other. It may take a lot longer to do it this way but it is worth the effort. I won't say that all this reduces the trigger pull much if any but it does make the trigger feel much nicer. I believe just adding a good teflon based oil to the pin is enough in most cases. I did not remove the magazine safety or the gun safety lock device below the hammer strut. A special thanks to Wrangler for doing the first trigger job and letting me know how he did it. One note about lubrication upon re-assembly. I found any part that was polished and had oil applied to it the oil just slid off. I used Slide Glide light on those polished surfaces and it stayed put. TW-25b worked at first but it tends to dry out after a few months and makes things worse. On surfaces that are not polished a good Teflon based oil should work well. You really only need to lubricate the places where there is metal to metal contact of moving surfaces. For those that can't find their owner's manual you can download one from Sig http://www.sigsauer.com http://www.sig sauer.com/upFile...MOS /upFile...MOSQUITOUSMANUAL QUITOUSMANUAL.pdf  .pdf  Near the end of the manual there is a parts break down and in this format you can increase the size to see more detail. When using a hone or other abrasive it is important to move in the direction the two metal surfaces will be in contact during normal use. Normally it will seem faster the go a different way or use rotory tools but you will probably be doing more harm then good. Rotory tools make nice

waves in metal and not good flat surfaces. Breech Block Removal 1. Remove the slide 2. Remove the hex screw on the right side safety lever. 3. Slowly push the shaft of the safety lever to the other side. There is a very small ball bearing and spring that keeps the lever in either the on or off position you will need to capture. 4. Turn the windage adjustment screw of the rear sight counter clockwise until the sight no longer moves. You will have to have the slide with the sights up and the block down. This is just like it will normally sit on the pistol. Try to keep it fairly level. push the rear sight a little more with your thumb and the breech block will loosen. 5. Move the rear of the breech block down a little then forward to release from the slide. Keep the block assembly level. There are springs and at least one pin you will need to know how they are now to put it back together again. I highly suggest taking pictures at this point. The firing pin and extractor are held in place with pins that will need to be driven out to replace these parts. The spring for the firing pin will need to be compressed with a small tool to get the firing pin back in place. The firing pin does need to be rotated up to clear the end of the block  assembly. Reverse the process to put it back together again. I don't recommend taking this assembly out unless there is a real need. For this reason I did not provide the pictures I took to allow me go get mine to work again. Using a little grease like Slide Glide Light to hold pins, bearings and springs in place worked for me to make re-assembly much easier. Wrangler provided the Dis-assembly portion of this thread. I did the Re-assembly part. Without Wrangler's help none of this would be here in the first place. The old Mosquito fixes thread has been reposted on a different site. It probably will stay available there much longer then it will here. I understand and agree with the policy on this site reguarding inactive threads. You can find it at this address: http://www.rimfirecentral.com/...wthread.php?t=386450 Happy shooting.