Rumour I heard, is that Canada is on the list of countries that harbour terrorists, and 7.62x39 is a "terrorist" round.
Ergo, no US made ammo or ammo of any sort of that calibre can cross the border. Why you don't see any Winchester or Remington SP ammo in that calibre, and why you see Euro surplus here instead.
Dosen't have to make sense.
The former Liberal governments P****d off the Americans so we now have to pay for it.
The following countries are exempt for US export permits for ammo etc...
Australia, Belgium, Bulgaria, Czech Republic, Denmark, Estonia, France, Germany, Greece, Hungary, Iceland, Italy, Japan, Latvia, Lithuania, Luxembourg, Netherlands, New Zealand, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Turkey, United Kingdom (excluding Ireland).