Grey, please never order an upgrade or accessory for your guns, as you would be committing a crime by paying someone to have made you a part.
The above is a description of making individual pieces for guns. Making a RAS/RIS unit is not illegal, making a mock silencer is not illegal ((unless it can affect a REAL gun)). Only if he starts making products that would fit and operate real steel to enhance its firing capacity/power/ or decrease its sound volume would it be illegal.
Also, no where above does he state that he is interested in machining an entire gun. If all he machines are accessories and parts for an already existing gun, then he's committing no crime as he is not producing anything that is not existing already.
"The hydrogen economy car from the people who brought you the 'Hindenburg
'" - Glen Foster
Condoms do not guarantee safe sex any more. A friend of mine wore one and was shot by the woman's husband!