Want to know the answer,,call, email or write the BATF Technology Div and put the question straight to them. Get the answer in writing if you are going ahead with the project on their say-so.
They interpret the rules and regs as they currently stand as to what is legal to own and do to a firearm and what is not.

Contact info w/ phone, email and address:

Firearms and Ammunition Technology | Bureau of Alcohol, Tobacco, Firearms and Explosives