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Thread: SGN-22 article

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    gunco irregular moleman's Avatar
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    Default SGN-22 article

    I couldn't find a thread specifically on the sgn-22 so I thought I'd start one. The sgn-22 is a single shot self ejecting design that I belive can be easily adapted to semiauto with a few changes. The bolt design my help those of us that want to make their own 22lr, 22mag, or 17hmr semiauto. While I don't think I'll make a sgn-22, I do think I may try making a 17hmr bolt for use in a standard ar15 upper with a 17hmr barrel using savage mags with an adaptor.
    The first article basically listed the concept and showed the receiver construction which is basically a tube with a ejection port with a 10-22 barrel turned down to fit. Part two shows more of the bolt design which uses a modified ar15 firing pin and an ar15 type plunger ejector. It looks promising so far.

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    Gunco Member TradeGun's Avatar
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    In part two, Matthews describes how to build the bolt. As I looked at the pics, I noticed that he has a recessed bolt face resulting in what appears to be feed lips. You might want to modify the bolt face to make it legal for a semi auto.

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    gunco irregular moleman's Avatar
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    If you were making a semi gun and going to keep the ejector pin then you would also have to keep the recessed bolt face and once cut to take a magazine the feed lips would have to stay there. The atf does take a dim view of tube guns with feed lips, but there are guns out there where it is acceptable. I read once that if the original gun had a fixed firing pin then the semi version had to have the feed lips removed. I don't know if thats true of not but it may have some merit. If you modify a suomi or sten bolt to semi then the feed lips need to be removed. There is a new made semi sten bolt that is baft approved and has the feed lips. Its really not needed for the most part except for designs like the sgn-22 that use a spring loaded ejector to eject the spent case. I think the only real way to get an answer of its legality is to write into the atf and ask them a specific question on a specific bolt design. Since there are easier designs out there to make that don't have a feed lip or ejector pin which might get you in trouble I agree with you and would stay from his design. That was the "can be easily adapted to semiauto with a few changes" I spoke of earlier. I think the design would be much easier to make if it used a fixed ejector and had a bolt face similar to a ruger MKII shown below. If I was going to make the bolt as he did I probably would make it in 2 parts. The front part could be the actual bolt with the last 1/2" of it reduced and threaded for a like sized pipe to be screwed on or welded with cut outs for the hammer and the same 1/2" of it a solid ring where it connects to the bolt head.
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    Gunco Member TradeGun's Avatar
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    Moleman

    I agree, a fixed ejector is the way to go. I must admit that I am kind of taken with the simplicity of the SGN22 and am considering building one, although I am not too keen on the feed lip bolt. I'm thinking that if you cut a slot in place of the ejector tunnel on his bolt, you could user a fixed ejector and eliminate the feed lip.

    Of course then you would have to rework the firing pin return spring, but that shouldn't be to hard. I would probably use a Galil barrel and reline it as Sarco has them fro $2.00 each with bad bores.

    You might be on to something with the multi part bolt.
    Last edited by TradeGun; 04-26-2009 at 04:32 PM. Reason: Typos

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    gunco irregular moleman's Avatar
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    Quote Originally Posted by TradeGun View Post
    Of course then you would have to rework the firing pin return spring, but that shouldn't be to hard.
    You might be on to something with the multi part bolt.
    I'll admit I haven't sat down and drawn out the bolt yet, but if I went with his design for the firing pin and spring with a slot for the ejector why would I have to rework the firing pin return spring? I should be able to cut a slot in the bolt at least as deep as the plunger hole that he uses on the sgn-22 bolt with out cutting into the firing pin channel. I could just be all nyquilled up though! I thought it might be a lot easier and slightly cheaper to machine the bolt if it was a two piece. You wouldn't have to file the front of the cocking slot and use long extended drill bits, and if you messed up a front section you wouldn't waste as much of the good bar stock.

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    Gunco Member TradeGun's Avatar
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    I was thinking that the firing pin return would need to be reworked if I went with a fixed ejector because he used the same spring for the ejector plunger and the firing pin return, I hadn't thought about using the back of the fixed ejector as a spring keeper. Great Idea!!. The more I think about it, the more I like your multi part bolt. You could probably get away with mild DOM tubing for the back section.
    Last edited by TradeGun; 04-28-2009 at 07:38 PM. Reason: spelling

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    gunco irregular moleman's Avatar
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    See I was all nyquiled up! I'm going to go with a coil spring around the firing pin like I did on my suomi build. Its a simple coil spring .225" od, .168-9" id, 1.65" long .028" diameter wire. Since I'm building this for an ar15 I'll have to shorten the spring and just make a new firing pin probably the same length/style as my m261 22lr adaptor kit uses. You lost me on the "fixed ejector as a spring keeper" thing. If I get some time later on I'll put up some pictures of the m261 firing pin.

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    gunco irregular moleman's Avatar
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    Here's the bolt face and firing pin of the M261 22lr adaptor for the ar15/m16. Since the chamber insert brings the bolt back about .3" the firing pin is that much shorter than a regular ar15 pin. If I make a 22mag or 17hmr upper for my ar15 then I will use the same length firing pin as the M261 depending on how I run my magwell adaptor and how far back my barrel is in the receiver. The diameter of the bolt is .990".
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    Gunco Member TradeGun's Avatar
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    The Galil barrels came today. They were definitely rusty, but the bores cleaned right up and are nice and shiny! I sandblasted the the outside to clean them up. I think they will work nicely after I turn the barrel threads off.

    I'm thinking I can just reline the .223 chamber with a short piece of .22 rimfire liner, cut a .22LR chamber and use the original chromed rifling. This will eliminate the need to deep drill the barrel.

    I will try and post some pics

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    gunco irregular moleman's Avatar
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    That sounds interesting. For $2 thats a great find. I shoot 22lr in an ar15 (a lot more lately) and the larger .224" bore and long throat still provide acceptable accuracy for plinking.

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