Here in UK that's called 'gunsmithing' and if you are not registered as a gunsmith, you can be charged with 'feloniously producing a Section 1 Firearm contrary to the Firearms Acts of 1926, 1968, 1988, 1997 and 203, 4 and 5'.
This carries a maximum sentence of ten years for each part of the offence, an unlimited fine, and death by hanging, drawing and quartering, burnt at the stake, and get smacked by the archbisop of Canterbury. Not necessarily in that order.
Mind you, if you and your pal get together and drown a fine young man in a deep pool by stoning him until he loses consciousness, you may get away with ten hours community service, and a slap-up meal at the end of it.
Sorry, I'm being sarcastic here. :cursing:
tac