I have searched and searched to find information about what the ATF says about what is legal as far as permanent attachment of a flash suppressor or other device to reach or exceed 16" and thus not qualify as an SBR. Anyone help me out here?

i think it has to be silver soldered or some other type of welding/soldering.

Silver solder has to have at least 1100 degree melt point, or you can drill a hole through the FS into the barrel install a pin or set screw and weld over the hole.

I think he is looking for a link to the actual law.  I would like to see it myself.  I have searched all over the ATF site and can`t find it.  

However I did find some good information on the potatoe gun laws.  I think you can have a bayo lug on them now!

Steve

The best I could find was a letter to the technical branch.  Notice that this is addressing both the NFA and the AWB.  Blind pinning is not specifically mentioned here, but I would bet it is acceptable if covered by weld.

If you attempt anything else, you may want to write.

Letter 1

A muzzle device, such as a muzzle brake or barrel extension, which is attached to a barrel by means of welding or high temperature silver solder having a melting point of at least 1,100 degrees Fahrenheit, is considered to be part of the barrel for purposes of measurement.  A seam weld extending at least one-half the circumference of the barrel or four equidistant tack welds around the circumference of the barrel are adequate for this purpose.

Thanks all, I believe my question has been adequately answered, the link Southern_Raider provided was very informative. I have seen many "permanent" attachments done via a pin, cap welded in place, according to this info that may not be acceptable.

I think I will be forced to go the silver solder route as it seems the least destructive of the three. With the required melting point of the solder being 1100 degrees that’s still 1600 degrees lower that the melting temperature of steel so I'm hoping I will not cause damage to my barrel, even though I am certain to cook off my finish.

Anyone have and other good solutions they have seen or used, or know anything about the resistance of the phosphate coating used on barrels and flash hiders?