I would buy a K-31 right away if you are interested in one. They won't be around for very long. 5 years ago, they couldn't give these rifles away because noone knew anything about them or where to get ammo for them, in the last 2 years or so, they have become very popular and I doubt that wholesalers will even have them available a year from now- even the surplus ammunition for them is vary hard to find.

The K-31s are very accurate rifles, capable of shooting as good as or better than any factory remchester on the market right now with a few tweaks or modifications. Even the surplus 7.5x55 ammunition is match grade and is capable of shooting 1moa or better with these rifles.

As to why straight pull rifles aren't commonly made, is that they are more expensive to make, are more mechanically complicated than, and don't offer any great advantages over a standard bolt action rifle. There were a few other straight-pull rifles made- 1889, 1911 Schmidt-Rubins (the ancestors of the K-31) Steyr Mannlichers, Canadian Ross', and a more recent rifle known as the Mauser model 96 (not to confused with the Mauser 1896). The Schmidt Rubin/K-31 series of rifles were by far the most mechanically complex and precisely made out of the whole bunch- noone could afford to build rifles like this anymore- or more likely, noone would be able to afford a rifle made like the Schmidt-Rubins/K-31s if they were made today.