Read the Fucking Manual
Since we don't have a 'manual' per se... What Garcia said... but there's a thread right now in the trash about someone's metal MP5 bodies getting seized, and getting a visit from the RCMP too.
The barrel, I dunno actually.
Buy from in Canada. Meaning, a Canadian site or supplier with the product in question already in Canada. Saves you the hassle and worry.
"War must be, while we defend our lives against a destroyer who would devour all; but I do not love the bright sword for its sharpness, nor the arrow for its swiftness, nor the warrior for his glory. I love only that which they defend: the city of the Men of Numenor, and I would have her loved for her memory, her ancientry, her beauty, and her present wisdom. Not feared, save as men may fear the dignity of a man, old and wise." - J.R.R. Tolkien