In before "I just brought 500 rounds of X back with me, no problems..."
Short answer:
Canadian regulations say that yes, you can bring up to 5000 rounds back with you.
US ITAR export regulations will nail you to the wall for a single empty .22 casing, along with firearm parts and accessories. Reloading presses and dies fall under "tools" and are exempt, except for the automated (turn on and walk away) high-volume type of machines.