Before entering Canada, stop at US Customs and declare your equipment, there is a form for this. So when coming back, you have proof you brought it in and no taxes are due. I go up to NW Sascatchewan moose hunting and do this everytime. And as mentioned, there are Canadian forms needed to bring an acceptable firearm into their country. I've even been questioned about ammo, we enter by Minot (Antler), don't know if that's standard or just specific to that border services agency or that particular agent. Enjoy and best of luck to you!
Ammunition may be imported duty free up to 250 rounds per person, unless the total has changed recently. Big game hunters rarely have an issue with this, but waterfowlers sometimes bring more. Sometimes customs asks about this and sometimes not. The duty, if any, is small and it sure beats trying to find your favorite loads up there.
I’ve often read about declaring your expensive gear at US Customs before you leave, but I’ve never done this and it’s never been an issue on dozens of trips. I’d be curious to hear if others have had issues with this. Once we were stopped by a Fed while leaving and his question, with a bit of an attitude, was: “What do you have with you?” I looked at my truck; full to the gills with gear and dogs. Then at my trailer, with ATV, layout blinds and at least 4,682 decoys, and just said: “You must be joking”. I told him I had my duck hunting stuff. He took that answer and sent us on. If I’d tried to itemize it for him, we’d still be there! 😳