I just did this last summer (and a couple years ago). You need a Non-Resident Firearm Declaration Form (RCMP 5589). If you can't find it, send me a PM and I'll try and send you one as an attachment. But if you scroll down on the link below, you'll find it:
http://www.rcmp-grc.gc.ca/cfp-pcaf/form-formulaire/index-eng.htm#f5
A couple pointers:
1. They tell you you need $25 in CANADIAN CURRENCY when crossing the border to declare your weapons. That means HAVE $25 EXACT CASH IN CANADIAN CURRENCY ON YOU WHEN YOU SHOW UP AT THE BORDER!!!!! Don't think they will exchange US currency there, make change, or you're smarter than them. You want your border crossing to be as painless as possible. HAVE THE $25 CANADIAN CASH ALREADY IN HAND WHEN YOU GET THERE. Don't over think this, or think they'll take a credit card or something. They've heard it all. HAVE THE $25 IN
EXACT CANADIAN IN HAND BEFORE YOU CROSS OVER. Can I make this any more simpler?
2. They may not want to see your weapons when you cross (I've had them not ask, and I've had them want to see them). Have them readily accessible when you get there so you don't have to go digging for them just in case. And have weapons unloaded of course at the border.
3. Be very polite with the border folks. Look decent at the initial crossing; not like a meth-head or a bum. It is their country - their rules. You just want to get through it. They've always been very polite to me (and I've gone up there more than once, and criss-crossed borders even more on just one trip [Alaska - Canada - Alaska - Canada - WA]). And remember if asked - you are bringing weapons in for protection from wildlife only.
4. They mean business at the border. Don't think you can hide a handgun somewhere in your vehicle. They might be bored that day and decide they're going to check every nook-and-cranny on your vehicle. They know all the hiding places - that is their job. Bad things will happen if you get caught with something you shouldn't have. We got delayed once at a remote border crossing into Canada because they were arresting someone trying to bring something across they shouldn't have.
5. Of course, have the forms fully filled out neatly BEFORE you get to the border (typed is probably better). Follow the instructions on the form to the letter(!).
6. After you leave the border crossing, put the signed and stamped form(s) in a very safe/dry place where you know where it is, and where you can access the form if you're asked to show it. We had a three-ring binder with clear document protectors that we traveled with that stored all important papers.
The guns we brought into Canada have included a short-barreled H&R Pardner 12G pump shotgun with bear slugs (google "Dixie Slugs"), a Marlin big-loop lever action guide gun in 45-70 (with bear rounds - google "Garrett Cartridges" and their Garrett's 45-70 +P Hammerhead Ammo), and a Rossi model 1892 44 Mag lever action carbine in stainless steel. Of the three, the 44 Mag would probably be the least effective on a pissed-off bear (but is the one I literally slept with along with bear spray close by). Bear spray is also your friend in Canada (and don't go cheap on the bear spray). Buy the bear spray holster if it is an option. Everyone in your party should have their own can of bear spray (and on their person).