The K31 is a straight pull action. It is not a Mauser. You can find K31s in the Shotgun News. I will send you some addresses and phone nos. soon.
The K31 is probably the nicest made rifle ever. I have a Rolex watch that is crude by comparison.
The blueing, fit, finish and machining are all absolutely exquisite.
Now I have to go and take a cold shower. Just thinking about that beautiful Swiss miss is getting me all hot and bothered.