I helped a friend with some logistics for on a Cowboy Action shoot last month. Several
Canadians attended. One fellow told me some of the differences
between Canada and the US. In CA he was allowed handguns with
barrels 4" or over, while in the US you can own shorter. On the
other hand he could own in Canada a short barreled rifle or
shotgun, whereas in the US they are restricted and even in "free"
states they require a Federal tax stamp. He said he owned short barreled AR type rifles. (Just looked online and see
the short barreled long guns do require extra paperwork in
CA)

Even bringing firearms across the border wasn't a big deal as long as the paperwork for both countries was done in advance.

As Cowboy Action shooters, they brought single action revolvers,
shotguns, and lever action rifles. They cast their own bullets
and loaded their own cartridges.

If I remember right, he was from BC.

They were a friendly bunch, some were firearm dealers. You might
find a club like that to visit for more insight.

http://www.cascanada.com/casalberta/index.htm

http://www.cdnshootingsports.org/rangemaps.html