Said another way, you make your money when you buy, not when you sell. If you are looking at this as an investment (ie, getting more than purchase price back), you will be competing with a lot of dealers and sophisticated collectors looking to do the same thing. That means a lot of time in the market trying to find that good deal before they do. And if you do find that good deal, shooting your investment is risky because you will likely degrade the original condition of the gun and be putting it at risk of something more catastrophic (broken stock, dented barrels).
If you are looking for a shooter that has a good prospect of being resold for what you paid for it, that opens the field up more. You might want to peruse some of the recent UK and US auction results to see what has been fetching the best prices recently. Doing that however, assumes that the "market" will be the same 20-30 years from now. Who knows - maybe Churchill XXVs and Scottish boxlocks will be all the rage to the next generation of collectors. Who in 1980 was predicting the current market for vintage sxs?
