The ATF notified licensed dealers in writing of its stance on work done to silencers already entered in the national registry. Dealers may fix a finished silencer or switch the caliber it can handle without the job counting as production of a new NFA item, so long as the serialized housing stays whole, required stamps stay readable, and no extra firearm results.

Prior advice allowed one-for-one swaps of broken inner pieces without fresh tax or paperwork if the outer tube remained. Lengthening the unit by adding baffles or boring existing baffles for a bigger round had created extra parts that themselves needed marking and listing. The agency now treats the unit as the original registered silencer whenever its serial number is left untouched.