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Sig Mosquito Tip

Discussion in 'Handguns: Autoloaders' started by Mark13, Jan 27, 2013.

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  1. Mark13

    Mark13 Member

    Mar 3, 2004
    I purchased a Sig Mosquito to have an easy to shoot autoloader for my family.

    Purchased a 525 box of remington golden bullets .22lr to shoot. Never used those before

    I disassembled/cleaned it and was excited to try it out.

    Right off, I was getting ~40% light strikes that fired on the second pull. No cycling/feeding issues.

    Online, I noticed that the remington bulk .22 was getting a bad rap, and that the mosquito also was noted for more than occasional light strikes.

    I was disappointed, and afraid that I had purchased both bad ammo and a less than quality .22 handgun.

    I like to mess with things so I disassembled the breech block and examined the firing pin.

    The tip has two lobes upper/lower on the part that contacts the casing. The lower has a rounded face and strikes the rim. The upper lobe appears to be an overtravel stop that was contacting the rear of the barrel, just over the top of the case rim at 12 o'clock.

    Given the width of the .22 case rim the upper lobe appeared to be too long. Also the face of the upper lobe was not flat, it was ground at an slight angle, like a chisel. I could see a matching chisel like indentation on the matching 12 o'clock position on the rear of the barrel.

    The firing pin looked stamped, and the tip is tiny. I think it was a defect in the firing pin finishing process.

    I took 400 grit wet sandpaper and rubbed the tip of the firing pin perpendicular to it until the upper lobe was flat and only extended only a tiny amount past the lower lobe.

    I reassembled and fired 60 more shots. Only 1 light strike that fired on a second pull. This seems acceptable given the low quality ammo I was using.

    I hope this helps someone who purchased a Sig Mosquito and getting light primer strikes. It's a easy fix, if your firing pin was not finished correctly like mine.
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