That non-resident declaration is for long guns only. Handguns are forbidden in Canada except for the CRMP's. Period.
I can tell you from a LEO point and travel to Canada for both work and personal reasons, I can't even carry a handgun into canada. And I can carry everywhere except Canada!!!
They meet us at the one of the crossings, we declare and secure our weapons, are ******ed to our destination, pick-up whom ever we are bringing back after they have apprehanded, or we perform our surveilance and they apprehand for us in a joint task operation, and back home we go to pick up our weapons crossing back into the US.