Crossing the line.

[Ol` Joe]

I`ve carried rifles to Canada a few times hunting. As said handguns are a quick trip to jail, as I recall handgun ammo is also frowned on.
You need to register long guns on the US side as well as declare them on the Canadian. The BP needs to know they came from the states and you`re not smuggling them when you try crossing back home. The registration is a one time per gun thing and is good for ever once it`s done. Personally I think it`s as good an example of "back door registration" as you`ll find.
http://www.cbp.gov/xp/cgov/travel/va...d.xml#Firearms