Not even 1% of the population of CA hunts. South Dakota, with a population of less than a million, sells almost as many hunting licenses as CA. And steel shot has become quite affordable. I doubt the CA lead ban will do much to give us nontox alternatives to steel that are both reasonably priced and suitable for use in vintage doubles.
As for doublegun prices, I think Brit boxlocks have been bargains, relatively speaking, for quite some time. And I haven't noticed prices on Stevens going up much except for the smallbores, especially .410's. If you own an American .410 sxs in decent condition, regardless of the maker, it's going to be worth a fair chunk of change.
