To add to my previous post... Guns can be an investment, or an expense.
If a buyer is savvy he can make purchases which will prove beneficial in the future. There are some guns which will go through the roof, and some that will be worth what you paid for them.
Usually, it is the unusual, or very high end guns that become worth money. IMO, my Ruger P97 will never be worth more than $400. I paid $360. With inflation, not much of an investment. However, I have 2 Colt Pythons that I have less than $1000 tied up in. Go to gunbroker to see what they are going for now.
With rare exception, a working man's gun like most Rugers are not going to become a collectors dream in the future. As much as i like Rugers, they are a working gun, not any thing collectors grade (again, with a few exceptions). What you should be looking for, is a small run of guns that turn out to be unprofitable due to the cost of manufacture.
Some of the most sought after collectables are guns which failed due to manufacturing costs, namely, most Colt revolvers, pre-64 Winchesters, and other high end guns.
Can any of us tell the future? Like the stock market, no. However we as gun guys, can look at a gun that seems unique, and of higher quality than seems likely given the price point. THEN, such a gun is a likely investment.
At the worst, guns are like gold... They may never be worth as much as you paid, but as long as they work well, they will always be worth something.