I call Scam
I have done several transactions on Gunbroker and many on eBay over the years. One thing I have learned is that honest buyers and sellers work very hard to make sure every transaction goes perfectly. They over communicate consistently, in a positive way.
In my mind, anyone who would fail to provide you a correct shipping address is trying to pull a fast one. When you add in his negative feedback from previous transactions, I see no room for doubt about his motives.