regarding export of ammo from US to Canada: Canadian law allows for import of a significant quantity without a permit, but the US requires an export permit. As Tamid experienced, unlikely that Canadian Customs would be concerned about the US export permit being in order. The chance of getting checked by US customs on departure is clearly very low, but departure checks do occur and I would imagine that the potential consequences could be extremely unpleasant.
If on a hunting trip I wouldn't think a small quantity left over would attract any attention coming back.
Would be great if someone picked up distribution of RST in Canada, but on the other hand with the current exchange rate it would make for pricy shooting. I recently bought a 2 1/2" gun and after looking at the limited options in Canada, decided to try my hand at reloading.
Do not underestimate the enthusiasm for which American ATF and Customs agents pursue the illegal EXPORT of ammunition. They have been observed writing down plate numbers at gun shows and big box hunting retailers so that they can follow up with a more detailed examination as you attempt to leave the country. Given the penalties it is a high risk activity with a downside far worse than the potential upside.
As noted, the Canadian authorities couldn't care less unless it is more than the 5000 round limit.
I have actually contacted RST about export to Canada (I was a sporting goods distributor for many years) and they were not interested in the headaches involved with export. Happy just servicing the US market.
