Again I would have to agree with Jack. The Holographic sites are fun to fool with (got one on a collapsable stocked, 16" barreled AR) but to take advantage of the accuracy you can get out of the K31 (and I have yet to find one that wasn't accurate) you need to put a scope on it.
If ya just wanna have fun with it then go with the Holographic site, hey its ur rifle and that means you can do what you want. But just because these things sell fairly cheaply do not underestimate what they will do at 100 yards and beyond.
My advice would be, if you are looking at saving some $$, put a scout mount on it and find someone with an extended eye relief scope or better yet a pistol scope (4 power will do) then take it out to your nearest 100 yd range with the suplus ammo that is now available for it (it is really good stuff and constent) THEN make your decision as to what you wanna put on it.
To me, and this is just my opinion now, putting a holographic site on a decent K31 is like never driving a crotch rocket over 30 mph...
Jist one fella's opinion...
DonT