The fine firearm market is very strong right now. It gets stronger in some ways during a dire, disastrous economy if you don't buy lousy guns. (I'll define that later)
In good economies (like the present 10 years), demand drives up the price of new fine guns. This provides further support for the value of secondary market fine guns as their replacement costs continue to climb.
In lousy economies like 2008, there wasn't much in the realm of good guns on the market. It took 2-3 years of a crap economy to put enough financial pressure on the affluent to divest themselves of super premium best guns. In 2012 there were no less than 5-7 Westley Richards take down mausers on the market and at least 10 rigby 275s at a time. But once the economy improved, crap guns and limited supply was all that was available.
Right now for example, the guns that are coming through Holt's auction in London are just awful. Not a lot of stunning examples, just tired guns, oddly configured guns, and common caliber guns.
An excellent investment grade gun defined: Limited supply. Strong demand. Ideally a gun that is still in production to prop up the utility price for the person that isn't a collector but is contemplating a new best gun, but compromises into a vintage best gun of similar configuraiton. That's the best case scenario, when collectors want a gun, and so do non-collectors because its cheaper than buying new. Examples: Purdeys, Hollands, Westleys, Heyms, MacNaughtons, Dicksons, Hartman and Weis, Dakotas.
A lousy gun is a slice-in-time nostalgia gun that caters to a collector longing for their youth. I'm not a greatest generation or baby boomer, (I'm Gen X) so I didn't grow up with Cowboys and Indians fantasies. The elderly collectors are fixed-income pensioners, and they've amassed huge troves of Parkers (and their dreadfully and bizarrely priced Japanese replicas), Colts, old S&Ws, and lugers. Those guns are going to take a bloodbath, they just aren't worth as much or coveted as much by Gen X and Gen Y that have the working disposable incomes to justify such purchases.
But a best gun that has a contemporary demand? Those are going to do great.
Vintage Dakota for $12000 versus an identical parkwest for $17,000+? No brainer.
Vintage Boss 20 bore side by side for $30,000 versus a new one for $150,000? No brainer.
Vintage Grant or Lang for $15,000, versus a remanufactured one from AG&L for $60,000? No brainer.
Vintage Winchester Model 21 for $6000 versus a CSMC reproduction for $20,000? No brainer.
Vintage Westley Richards 318 for $8000-$12,000 versus a new one for $60,000? No brainer.
Vintage 1990s Heym Double Rifle for $15,000-$40,000 versus a new identical one for $28,000-$90,000? No brainer.
Vintage Hartman & Weis magazine rifle for $30,000-$40,000 versus a new one for $75,000? No brainer.