Last year I was smitten by the K-31s. Never paid much attention to them until last year. As with most Milsurps, I can't get over how much rifle you can get for such a reasonable price. I ended up with four of them.
As far as appreciated investment, (I have owned a variety of these "oldies but goodies" off and on for over 50 years) I don't consider them anything exceptional. Sure, you will find someone who will pay a pretty price for one, but in general, I would agree with Krochus that they tend to run with inflation. There are always exceptions, but I don't think our run of the mill imported milsurps are spectacularly good, or bad, investments for that matter. I once took some estimated prices of some of the imports that I have had over the years, what I recall paying for them vs. current market value, and I believe I guesstimated it at 4% - 6% annual appreciation. Certainly a lot of room for variances there, but I think you have to average everything out. Condition will leverage the value as always. I think American milsurps in some cases (M1 Carbines?) have climbed higher and faster, especially fine or rare examples.
I kind of thought K-31's might grow in value a bit more, because they are unique and high quality, and there is a smaller number of them. Also, the metal, at least, is generally exceptionally good. But I'm not planning my retirement around my having four of them.
Hey guys, just one personal comment from me. Everyone of you in this thread - I have enjoyed your inputs and learned something from you. I hate to see Jack go like this, as he is enthusiastic and knowledgeable, and has shared a lot through his projects and pictures. There are sure more important things to squabble about. Maybe today would be a better day if we sucked it up and invited him to stay.