I have ordered electronic ear muffs, cleaning kits, targets, shooting glasses, mag loaders, oil and gun grease, the list goes on and on. My USA shopping rule is simple, if i can legally purchase the items in Canada i am good to go. Amazon does not ship most items to Canada so i have them mailed to my Ameri friend for pick up. I order from Brownells as well, no problems with customs thus far and they ship to my door but the order must be $100 or less. I would much prefer buying locally but for example, Glock mags locally $49, Brownells $28, big savings are not found on all items but 40% less is not uncommon.
If you buy from Brownells use "Priority Post", usually costs $5.75 if the items weigh less than 4lbs. Never use UPS, brokerage fees are criminal.