I bought my IBM M1 carbine after they had already started going up in price and I though $800 was crazy expensive for it at the time, but I knew they wouldn't be getting any cheaper. Can't touch one for under 12-1500 today. Don't remember exactly what I paid for my FN49, but I know they've almost doubled since then. Same with most of my milsurps. I know my $99 Mosin has more then doubled (and that was a fluke - they had gone up already, but AIM Surplus had some come in at the cheaper price so I snagged one after having already sold some that I got for even less).Friends have said to me - How much would you have if you invested in some market? I don't know, but I never would have guessed that the SAR-1 that I paid $269 out the door would be approaching $1000, or the $300 MAK-90 would have an asking price nearing $1500. Or the SPAS-12 that I paid under $1000, or the Russian TIGR for $1000. Look at original Colt Python prices.
But unfortunately unless the stuff hits the spinning device, I doubt that any AR will double or even quadruple as some of my prizes have.