hmmmm….so you are anyone can cut a barrel blank shorter than 18 inches....I think the NFA explains this...
CC s. 84(1) “prohibited firearm” (d): If the barrel has been SHORTENED to less than 18″/457mm, after leaving the factory, “by sawing, cutting or ANY other alteration or modification” that forces the firearm into the “prohibited firearm” class.
NOTE: The firearm is NOT forced into the “prohibited firearm” class if it left the factory with the barrel at below-18″/457mm barrel length. I have, for example, a .22 rimfire semi-auto 30-shot rifle with a 9-3/4″ barrel, a .410 single-shot shotgun with an 11-3/4″ barrel, two 12-gauge pump-action shotguns with 14″ barrels, a .22 rimfire pump-action rifle with a 17-7/8″ custom barrel and a .223 calibre rifle with a 14″ barrel — AND ALL OF THEM ARE NON-RESTRICTED. THAT IS BECAUSE THEY EITHER LEFT THE FACTORY WITH THOSE BARRELS, OR WERE FITTED WITH FACTORY- OR CUSTOM-MADE BARRELS IN THOSE LENGTHS AT SOME LATER DATE, and were NEVER fitted with a longer barrel. One left the factory with NO barrel, and so a 14″ barrel could be legally fitted.