I have flown Westjet and AC with firearms. No issue with either except that AC charges double what Westjet does. $50 for WestJet, $100 for AC.
Just declare it on check in, fill out a form, ammo in a separate bag and you're good to go. I used a hard case and made sure it was locked with machine screws and nyloc nuts so that someone would need tools to open it (me included-don't forget your wrenches) if I wasn't around. Plus my case was sort of lower end on the quality scale and I didn't trust the latches to stay shut after seeing how they treat the luggage in airports. Everything arrived safe and sound and on the same flight every time I've done it. And I've done it more than most....