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What makes "permanently attached" extension

1K views 7 replies 5 participants last post by  nalioth 
#1 ·
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.
 
#2 ·
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_handbook/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furthermost end of the barrel or permanently attached muzzle device, withdrawn from the barrel, and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? ;)
 
#3 ·
Yes, they have google:grumble:. 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.
 
#7 ·
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?
 
#8 ·
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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