If I turn a barrel down to lets say O.D. to .525" and cut the threads out of the muzzle

device with an I.D. of .523" and use liquid Nitrogen to freeze the barrel tip and then

heat up the muzzle device and press it on, is that a form of permanetly attaching per

ATF?  That would be more permanent than welding. There would be no way to Remove

it without machining it off.

Your making this way too difficult.

I want to cut down a barrel from 14.5" or even 16"  to 13.7" and then permanetly

attatch muzzle device without welding.

Don't do it. ATF recognizes two ways to do it. Do it their way.

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Don't do it. ATF recognizes two ways to do it. Do it their way.

Which is pined and welded? That's the only way is to weld on your barrel?

Quoted: Don't do it. ATF recognizes two ways to do it. Do it their way. Which is pined and welded? That's the only way is to weld on your barrel?

Welding makes the two peices "one" and as such is then considered part of the barrel.


Press fitting just makes the two peices tightly fitting. Its like saying if I really tighting down that vortex so its super hard to get off is that ok? No.

Quoted: Don't do it. ATF recognizes two ways to do it. Do it their way. Which is pined and welded? That's the only way is to weld on your barrel?

or silver solder

and I used to work in an industrial machine shop, I regularly dealt with press-fit components, and I can tell you that a .002 press is not that tight, and I could easliy remove it with a small propane or mapp gas torch... try press fitting something with upwards of .010 to .015 press fit...which weighs somewhere around 2 to 3 tons

Well I guess my question has been answered. welding is the only way.  thanks.  

A press fit, or shrink fit is not permanent.  You can always heat the Outside part while cooling the inside one to separate the two.  I don't know if ATF would approve this next method, but it would be impossible to remove without machining and no significant heat required to install:

Machine the two parts with a slight interference fit---a true press fit (~0.0002").  Cut matching grooves in the I.D and O.D.  Fit a spring washer (much like piston rings used in cars and the AR bolt) that is the same width as the grooves (0.001" clearance). Install the spring on the barrel and compress it when you press the flash hider.  The spring washer/piston ring will snap into the matching groove in the hider.  

The two will now be impossible to separate without machining off the hider.  Heat and refrigeration of the two parts will still not be enough to allow the parts to separate; it will allow the hider to be rotated if needed, however.  Note:  the shoulders of the grooves and the washer need to have next to no chamfering as a radius or chamfer might allow for shimming the spring washer and allow removal with temperature differential.

Blind pin? Relatively inconspicuous and legal.

The BATFE has the standards they require.  
 1.  Welded:  4 spot welds 90 degrees apart
 2.  Welded:  1/2 the circumference with a continuous bead
 3.  Blind pinned and welded
 4.  High temp, (1600 degrees) silver soldered.  And this better be done properly, If some gorilla at BATFE can wrench your muzzle device off, it was not permanent.
   They specifically forbid any chemical bonding

Quoted: The BATFE has the standards they require.    1.  Welded:  4 spot welds 90 degrees apart  2.  Welded:  1/2 the circumference with a continuous bead  3.  Blind pinned and welded  4.  High temp, (1600 degrees) silver soldered.  And this better be done properly, If some gorilla at BATFE can wrench your muzzle device off, it was not permanent.    They specifically forbid any chemical bonding

Probably the best all around method. Less heat to the barrel end, and doesn't show afterwards.

14.7" w/ pinned & welded A2 Flash Suppressor. CMMG's work.