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Thread: What makes "permanently attached" extension

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    Gunco Veteran nkluksda's Avatar
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    Default What makes "permanently attached" extension

    I'm nearly done with my SAS Sten Mk 3 kit (nice conversion kit, BTW), and I hit a nagging question.

    What constitutes a 'permanently attached' extension? If I weld onto the barrel, that's fine, but my welding skills aren't super, and I'm worried about damaging the bore. What about welding the extension onto the front trunnion? Does that count? The whole reason I ask is that I'd like to remove the extension when I get the paperwork done and approved for an SBR, and I don't want a junky barrel or damaged barrel. Welding on the front trunnion would be easier to clean up for an SBR if that's legal.
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    Gunco Veteran Markp's Avatar
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    You can use a silver solder with 1150 F or greater flow temp, weld it (tack welds count), or use a blind pin. Silver Solder is the easiest method.

    http://www.atf.gov/firearms/nfa/nfa_...k/chapter2.pdf

    "The ATF procedure for measuring barrel length is to measure from the closed bolt (or breech-face) to
    the furthermost end of the barrel or permanently attached muzzle device. Permanent methods of
    attachment include full-fusion gas or electric steel-seam welding, high-temperature (1100°F) silver
    soldering, or blind pinning with the pin head welded over. Barrels are measured by inserting a dowel rod
    into the barrel until the rod stops against the bolt or breech-face. The rod is then marked at the
    furthermost end of the barrel or permanently attached muzzle device, withdrawn from the barrel, and
    measured."

    Mark

    PS - Don't they have google where you live?

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    Gunco Veteran nkluksda's Avatar
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    Yes, they have google. And I've read the regs that specify HOW it should be mechanically attached and HOW the barrel length is measured. The question is more of WHERE does the extension need to be attached? The extension that came in the kit is a bit too large for a good brazed joint (a few tens of thousandths over what would make a good brazed joint, actually). But if I can weld it to the trunnion, it's an easy weld, it won't harm the barrel, and it'll be easy to clean up when the paperwork is done. If I have to weld it to the barrel, it's a bit more difficult.
    Q - What is Bambi?

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    BANNED nalioth's Avatar
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    Quote Originally Posted by nkluksda View Post
    Yes, they have google. And I've read the regs that specify HOW it should be mechanically attached and HOW the barrel length is measured. The question is more of WHERE does the extension need to be attached? The extension that came in the kit is a bit too large for a good brazed joint (a few tens of thousandths over what would make a good brazed joint, actually). But if I can weld it to the trunnion, it's an easy weld, it won't harm the barrel, and it'll be easy to clean up when the paperwork is done. If I have to weld it to the barrel, it's a bit more difficult.
    A barrel extension must be attached to the barrel.

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    Gunco Member old guard dog's Avatar
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    Good question. I think they would want it attached to the barrel, but it may be worth a call to ATF.

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    BANNED nalioth's Avatar
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    Quote Originally Posted by old guard dog View Post
    Good question. I think they would want it attached to the barrel, but it may be worth a call to ATF.
    The law says that the "barrel" must be a certain length.

    A shorter-than-legal-length barrel, hidden by an external shroud, is still illegal.


    Whatever is used to bring the barrel to legal length must be permanently attached to the barrel.

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    Gunco Irregular Grendeljaeger's Avatar
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    Nailoth does that include the front gas block/front sight base on an AK 102 style short barrel carbine? I'm not trying to muddy the water but I'm curious. And if you blind pin the gb/fs base to the barrel 1st does that change things?
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    BANNED nalioth's Avatar
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    Quote Originally Posted by Grendeljaeger View Post
    Nailoth does that include the front gas block/front sight base on an AK 102 style short barrel carbine? I'm not trying to muddy the water but I'm curious. And if you blind pin the gb/fs base to the barrel 1st does that change things?
    Here is an AK-104:



    Here is the FSB/GB:



    If you don't install the FSB/GB properly, your gun will eventually fail. Installation of the FSB/GB has nothing to do with legal length, and everything to do with proper functioning of the gun.

    If Johnny Revenuer can pull your muzzle device off with a wrench and a cheater bar, you are going to jail for an untaxed NFA gun. This is why you use one of the 4 approved methods of permanent attachment.


    If you're gonna install your 4.5" muzzle device with a blind pin on a rifle with one of these FSB/GBs, I'd suggest you blind pin it after the FSB/GB is installed.

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