The current younger generations don't care to waste time and space storing firearms that don't get used.
They'd rather have things that are affordable and usable (without consequences involving lost value).
The "Old Guard" are still swapping, trading, and going full tilt at auction, to complete their collections as their peers pass away and items come up for sale.
But, overall, in my opinion... We're nearing the end of wide spread, prolific gun collecting. As the boomers kick off and the market gets saturated (even flooded, by current standards), a lot of previously 'collectible' commercial firearms are going to be dropping in value.
Coins are a great comparison. Millenials ask the question: "What does it do?" What good is a coin in a plastic case? What good is an old revolver that sits in a box? What good does it do to have six hundred pounds of wheat pennies? How much fun can be had with a rare Winchester that does nothing but sit in a dark safe?
Mil-surps are a little different, though. There's been a resurgence in mil-surp collecting, with values still increasing. Notable modern films and shows about historic battles and wars certainly have some influence in the trend. But I think this also comes back to the "affordable and usable" concept. Mil-surps generally have wear and some evidence of abuse, with common but decent examples still being relatively affordable. As long as you don't Bubba, sporterize, or blow up the firearm, it retains its value while allowing you actually shoot and enjoy it.
To paraphrase an acquaintance's recent comments: "Why would I buy a two or three thousand dollar Python or Winchester that I can't touch, when I can get three or four, or six, really cool mil-surps THAT I CAN SHOOT?"
When I was younger, I collected PEZ dispensers.
I recently decided to dispose of them. There is, however, almost no market for them any more - not even the rare stuff. (Only the ultra-rare is worth selling.)
So, as I type this, I'm looking across the room at a box of targets for a future shooting trip. It is mostly full of PEZ dispensers...
