While guns DO appreciate in value over time, they SELDOM keep pace with inflation unless they are MINT - only those guns which were very rare or expensive to begin will ever make you any money.
E.G - a S&W revolver which cost $55 in 1950, would be like paying $500 for one today ... and MIRACLE of MIRACLES, that is about what their base line models sell for today.
E.G - A Beretta Jaguar, made in 1959, listed for $45... These days, a very clean example will sell for about $350 - even this somewhat rare model only outstrips inflation by 8% TOTAL over the last 52 years... that is SIX YEARS for a somewhat rare gun to appreciate 1%.
Even very (artificially) rare guns like full autos haven't actually appreciated by that much - a $400 machine gun purchased in the early 80's would be the equivalent of several thousand dollars today - THAT'S why so few were sold back then... $300 - $400 was a HECK of a LOT! Such guns may have doubled or even tripped over their inflation adjusted prices thanks to their artificial scarcity, but even most of THOSE have not managed to produce more than single digit value appreciations when you account for the DECADES it took to get to that point.
Unless you plan to invest in gold plated Lugers, then reality is you will likely only break even by "investing" in guns.
You would be better served buying savings bonds. 
The likelihood of you ever making any real money off of a few spare SKS is pretty low, barring a permanent ban.
My advice to you would be to keep them if you like them... otherwise, sell them now and buy something you like better. You have to be in it for the fun, because there really isn't any money to be had.
