It seems to me that sales of SXS guns, particularly 12 ga, have really slowed in the last five years. Maybe it is a continuing slow down along with the aging of the US population...Whta,s your experience?
One way to shield yourself from large depreciation is to buy only relatively new guns from the likes of: Purdey and Holland & Holland. Let's assume the worst and government agency officials mandate non-tox shot for all shotgun hunting you would still be covered because people that buy such guns can easily afford $60+ for 25 pack of Bismuth shells. I would not be surprised if newest high grade guns from England have steel shot proof and can be shot with variety of modern lead-free shot. Naturally if non-tox mandate comes to fruition used gun market will be flooded with old inexpensive doubles.
