[mrerick]

Looks like anyone that modifies gun parts will have to register with the US State Department at the cost of $2250 every year.

Registration Required
–
Manufacturing: In response to questions from persons engaged in the business of gunsmithing, DDTC has found in specific cases that ITAR registration is required because the following activities meet the ordinary, contemporary, common meaning of “manufacturing” and, therefore, constitute “manufacturing” for ITAR purposes
:
a) Use of any special tooling or equipment upgrading in order to improve the capability of assembled or repaired firearms;
b) Modifications to a firearm that change round capacity;
c) The production of firearm parts (including, but not limited to, barrels, stocks, cylinders, breech mechanisms, triggers, silencers, or suppressors);
d) The systemized production of ammunition, including the automated loading or reloading of ammunition;
e) The machining or cutting of firearms, e.g., threading of muzzles or muzzle brake installation requiring machining, that results in an enhanced capability;
f) Rechambering firearms through machining, cutting, or drilling;
g) Chambering, cutting, or threading barrel blanks; and
h) Blueprinting firearms by machining the barrel.

The specific document that lists activities is at:

https://www.pmddtc.state.gov/complia...ufacturers.pdf