basically any thing liek stock, mags, optics, u cant bring back..
depending on what reloading gear your after you might get lucky, since they are sold as "tools" not fire arms parts... that being said you will be hard pressed to find a store that will sell things to you. any where close to the border they will want to see some kind of proof of residency. hell my parents just went down threw the states and i asked to see if they could find a double sided gun case for me... plenty of them down there, but stores wouldnt even sell them to canadians.. thats right glorified suit cases wont be sold to canadians
long story short, export from the US is illegal but import to canada isnt..