Ok a lot of people are still not getting this, so here are the rules for cutting the barrel on your long arm simplified.
Anyone can cut the barrel of a semi-auto firearm, regardless of class, to no less than 18.5" (470mm).
Example: You cut the barrel on your M-14/AR-15/VZ 858/REM 1100/AK-47 etc. to 18.5" it is still legal. Cut them below 18.5" and they are PROHIBITED.
Anyone can cut the barrel of a non-semi auto firearm (single shot, bolt action, break action, pump action), regardless of class, to no less than 18" (457mm).
Example: You cut the barrel on your Win M70/REM 700/Mossberg 500 etc. to 18" it is still legal. Cut them below 18" and they are PROHIBITED.
NOBODY can cut barrels below these limits, period.
Nobody can cut the barrel of a restricted rifle/shotgun below the defined limits (18 or 18.5"), even if it is already below these limits, doing so creates a PROHIBITED firearm.
Example: You cut the 16" barrel on your AR-15 to 14", that firearm is now PROHIBITED.
Nobody can cut the barrel of a 12(x) prohibited rifle/shotgun to below the defined limits (18 or 18.5"), even if it is already below these limits, doing so creates a firearm that is PROHIBITED outside of the 12(x) classification.
Example: You cut the 16" barrel on your AK-47 to 14", that firearm is now PROHIBITED outside of the 12(x) class.
The only legal way to get a shorter barrel for your firearm (below the 18/18.5" limits) is to purchase, or manufacture one, at the desired length.
Example: You want a 16" barrel on your shotgun, the only way to legally do it, is to buy one that was manufactured at that length (not modified from a longer barrel).
Barrel extensions, such as flash hiders etc., DO NOT count towards barrel length, they ONLY count towards overall length (OAL).
If you have any questions about this or any doubts about this information contact the CFC and ask to speak to a firearms technician.