If the firearm is registered, and you want it deleted from the Registry as deactivated, you will likely have to follow the RCMP's deactivation guidelines.
These would include:
-boltface being cut back at 45 degree angle;
-hole drilled through the receiver and barrel breech, and a steel pin welded in place, welding both the receiver and the chamber.
-trigger mechanism rendered incapable of full auto fire by welding;
-firearm welded to prevent disassembly;
-magazine deactivated and welded in place.
I think that about sums it up. You can go to the RCMP Canadianicon Firearms Program website and look up the guidelines.