Are there any good pawn/gun shops around BR with old guns?

No

Cabella's has a great old/vintage gun room, but you better bring both your credit cards and check book, they not giving them away.

As far as pawn shops, anything rare/valuable, they are not going to put those out, they are going to sell them on the secondary market.

Are you looking for military surplus stuff like Mosins, Mausers, Enfields, and Garands? The few times I've seen things like over the years in pawn shops they were insanely overpriced.