The K-31 is _the carbine version._ Before that was the 1911 and it was a very long rifle. Not only was the barrel longer, the action was longer as well. A K-31 actually in the had doesn't feel long or heavy.
And like spence said, K-31's tend to be in excellent mechanical condition because they were issued to one soldier who took care of it and took it home. It is more like buying an old, well cared for hunting rifle than a military rifle. Most surplus has considerably worse bores than the K-31's. Although some of the K-31's have pretty bad stocks. The collectors claim it is because the Swiss left them outside their tents with their butts in the snow. So most buttstocks have quite a bit of water damage. They are still very sound or they would have been repaired but they don't look nearly as nice as the metal. Some people have done some very nice refinishing of the stocks. I did that to my early walnut model and it looks much nicer now. Although I tried to get it to still look "original." No plastic finish on my rifles!
For $89 and free shipping, what else are you going to buy, keep as long, and enjoy as much? You can't even buy a Ruger 10/22 at Wal-Mart for that kind of money!