I have been saving my brass on my 270 and 30-30 since I started shooting a year ago anticipating that I would get into reloading. Well, I have never found the time.

I have 500 of each and it will keep building obviously because I just love shooting the guns. Is it common for gun shops to buy these back? should I post on ebay? just keep saving them?
What could i expect to sell them for if in fact someone would want them?

If they are all the same headstamp and all fired just once, you might get 10 cents each - depending on the buyer. Usually are a little more marketable if they are all polished up in a tumbler.