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SKS piston

Discussion in 'Gunsmithing and Repairs' started by ChaoSS, Oct 13, 2013.

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  1. hang fire

    hang fire Member

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    If the SKS had been fired with milsurp ammo and not cleaned, or not correctly cleaned, (with water etc.) then piston may be corroded and froze in place.
     
  2. tnxdshooter

    tnxdshooter Member

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    It's great at cutting through crud. It's also a decent lubricant. It will really break a frozen bolt loose.
     
    Last edited: Oct 14, 2013
  3. ChaoSS

    ChaoSS Member

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    Well, the piston and the tube don't have the same numbers, and it seems that it was forced in. I'm sanding down on the piston a bit, and I got it to go back in, but it only goes down about half way. There's a little bit of an obstruction in the tube that I'm trying to sand out but it's not going too well, maybe I'll just sand down on the piston just a tiny bit more and see how it goes. I really don't want to have to buy a new tube/piston for the thing, although I guess I could get some parts that would contribute toward 922r compliance if I ever want a new stock for the thing.
     
  4. Miked7762

    Miked7762 Member

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    The SKS uses a short stroke gas system and the piston travels less than an inch to the rear when firing. If it is making it halfway down the tube before sticking it is more than sufficient.
     
  5. ChaoSS

    ChaoSS Member

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    Really? I figured that it had to travel at least as far as the little vent holes in the sides. How does it work then, just hits the bolt carrier hard enough to knock it back without having to actually push it back all the way I guess? I guess that makes sense though, the total length of the gas tube cylinder isn't long enough to push the bolt carrier all the way back.


    Now I just want to take this thing out and play with it. I've dry fired it a number of times just cycling it through making sure everything was working and the firing pin wasn't getting stuck forward, so I figure that means I cleaned that up well enough. Now there's nothing left but to take her out and shoot some paper.
     
  6. Miked7762

    Miked7762 Member

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    Yes, the operating rod strikes the bolt carrier and only inertia drives it back the rest of the way. The next time you have the gas tube out, push the operating rod back as far as it can go. That's all the movement the op rod and the gas piston have.

    If you haven't completely disassembled the bolt to clean it I would recommend that you do so. It's easy to do and if there was enough cosmoline to cause the gas piston to stick there's definitely going to be some left on the bolt internals. I can tell you from experience that a slam fire isn't fun.
     
  7. TimboKhan

    TimboKhan Moderator

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    Question asked and answered, but here is my two cents anyway:

    Cosmoline removal is a PITA. I have de-cosmoed a few guns, and the best/least effort solution was one I got of the old surplusguns site: I built a simple lightbox and let the bulk of the crap cook off. An even easier, but functionally identical method, is to leave it outside in a metal garbage can in the middle of summer. Provided you have a area secure enough to do this, it works and requires virtually no effort in getting rid of the majority of the cosmoline. Mineral spirits do a pretty good job on whats left over. I have even tried the gasoline method suggested in book two of "The Corps" series. More or less I just wanted to see if it worked, and it did, but the book also didn't lie about how dangerous it is. I had no issues, but it's the only time I have ever felt unsafe cleaning a gun!

    For the record, WD-40 is not a good lube, but it isn't a particularly good solvent either. Despite the "sticky residue" thing, my dad has done long-term storage on several guns for years and his only real trick is a liberal spraying down with WD-40 before they go in the case. All of those guns are in really, really good shape with none of this sticky residue. Not saying it's the greatest thing in the world, but the only empirical evidence I have to go off of suggests that it has it's place.
     
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