I buy quite a few firearms via GB and avoid sellers who have a "no returns" policy because if you make a bid knowing that they have a "no return" policy you're accepting those terms without any recourse. I also look at the sellers' reviews to see how previous buyers rate them.

I've had a couple of disappointing GB transactions, guns that were misrepresented, and made BBB complaints against the sellers because I know that GB won't do anything to help a dissatisfied buyer.