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Thread: Recoil spring modification

  1. #1
    Gunco Member SW44's Avatar
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    Default Recoil spring modification

    I think I have a good question for the experienced players on this forum. I am going to need to shorten the recoil spring when I attempt a gas operated 2xtm 7.62x25 conversion. (Just humor me, like I know what I am doing.) Does anybody have experience disassembling and reassembling that thing? I don't think I will need to shorten the rods inside the assembly, but I would like to hear techniques to do that in case I need to.

    You never have enough experience to not ask.
    Last edited by SW44; 09-18-2008 at 08:41 AM.

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    Gunco Maniac sjohnson's Avatar
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    Pull back on the spring, rotate the keeper out of the wire loop, release the spring.

    Assemble the spring on the wire loops, pull back on the spring, rotate the keeper into the wire loop, release the spring.

    It may be easier to say than to do, but that's how I do them.
    I have a daughter. I tell her, "911 is what you dial after you're raped. 1911 is what you should have before they try."

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    Gunco Veteran gunnysmith's Avatar
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    Before you shorten the spring describe the problem you're having.
    Shortening the spring can cause many different malfunctions.
    Failure to feed being one of them.
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    No Hope For Me 1biggun's Avatar
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    Before you shorten the spring describe the problem you're having.
    Shortening the spring can cause many different malfunctions.
    Failure to feed being one of them.
    correct to light of a spring and it wont be enough to strip the round out of the mag and lock in the bolt ect

  5. #5
    Gunco Member SW44's Avatar
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    No functioning problems yet because I am still fitting pieces together. I am using a PPSH 41 barrel and plan on moving the gas tapping location back to about 4 inches from the back of the chamber. I already made a "stubby" stainless steel gas piston and plan on sectioning the front tube of the bolt carrier so that the gas piston is in the correct location when the bolt is closed. This will result in the spring being more compressed in the shorter tube and put more pressure against the closed bolt.

    I plan on measuring the pounds force the spring exerts in a normal set up and then trim the spring bit by bit until it reaches the same level of force in the shortened carrier "neck". I think this will give me a starting point that can be adjusted if needed. Too much force and the bolt won't open, too little and the bolt won't strip a round from the drum.

    Thanks for the description sjohnson. I will try disassembling it tonight.

    By the way, my progress is very slow on projects so don't look for updates for quite a while. I am taking picture of the work as it progresses so there may be a story to tell later.

  6. #6
    Happy Camper hcpookie's Avatar
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    I would try the spring as-is and only shorten as needed. You may be surprised!

    Use a dremel cut-off wheel to cut the spring flat.
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  7. #7
    Gunco Member SW44's Avatar
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    You are right. You can always cut more off but putting it back ain't going to happen. Playing with the tools and experimenting with the design is the best part!

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    Gunco Veteran gunnysmith's Avatar
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    In gas operated pistol cartridge conversions, This is often overlooked as an alternative.


    This should be a camming slope rather than an abrupt drop off.
    Last edited by gunnysmith; 09-18-2008 at 03:57 PM.
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  9. #9
    No Hope For Me 1biggun's Avatar
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    sounds like a interesting project. keep us posted

  10. #10
    Gunco Member SW44's Avatar
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    Thanks for the tip Gunnysmith! I think I had read about that in a thread, but your pic makes it much clearer. I will add it to the bag of tricks.

    Unlocking the bolt a little earlier might also help with another concern I have. When the carrier moves back and before the bolt unlocks, I am concerned that the next round will try to move up into the space that opens up between the bottom of the carrier and the bottom "push" lug of the bolt. With a 39mm round that space is not too big. With a 25mm round it might slow the bolt assembly in recoil. Unlocking the bolt earlier might shrink that space at a critical moment.

    I am going to try the "minimal change" approach first and then slowly apply fixes if needed. The final fix is to go blowback!

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