My experience has been that you'll rarely get many deals at a pawn shop unless they don't know what they've got. Mostly you'll just be paying the going rate. In fact, most of the times, it seems pawn shops price their guns higher and so you have to work more to dicker them down to a normal level.
The advantage, it seems to me, is that you never know what comes through their doors. Most of their stuff is common and/or beat to crap but pawn shops occasionally get some jewels. It seems more and more these days, that when oldsters die off, many of their kids/grandkids have no sentimental attachments and just want to quickly get rid of his guns. So off they go to places like pawn shops rather than research the guns and get better prices at some auction or consignment venue.