Quote History Quoted:
Thanks for the quick response.
Do you have a link for that ATF guidance? My reading so far has been that the regulated part is the outer housing, since that is what bears the serial number, and thus the stamp, and that changing out the internals doesn't trigger a new stamp, much like changing out a barrel on a rifle doesn't require a new 4473.
It is entirely possible that I have been misinformed.
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The ATF defines the term “Firearm Silencer” or “Firearm Muffler” means
any device for silencing, muffling, or diminishing the report of a portable firearm,
including any combination of parts, designed or redesigned, and intended for the use in assembling or fabricating a firearm silencer or firearm muffler,
any part intended only for use in such assembly or fabrication.
http://www.atf.gov/content/firearms/firearms-industry/guides/gun-control-act-definition-silencer
The ATF also defines If alterations to a silencer would increase the overall length or change the diameter or caliber of a silencer, this is the making of a new silencer, as opposed to a repair.
http://www.atf.gov/content/may-repair-change-dimensions-or-caliber-silencer
Changing out the internals at a SOT for the exact same internals (Old parts to new parts) would not be a new stamp, but if the caliber changes then it's a new suppressor.
But all this seems like just knowledge sharing, as I'd venture to guess the bore size of the original suppressor in question is 7.62 or 7.63 to give a little more flexibility.
ETA: I I'm just a dumb redneck hillbilly, so take what I say with a grain of salt. I'm not pretending to be a lawyer or anything, just someone who thinks he knows something.