First off, I think the red and white bolt handles are just different materials, not different models.
When you chamber a round slam the bolt forward and then give it a rap to be sure it's seated !
The straight pull action got a bad reputation during WWI when stories circulated about Canadian Ross rifles that were fired with out the bolt fully locked and driving the bolt through the shooters head .
In his book "A Rifleman went to war" H.W.McBride, who used the Ross extensively in France, claims that was not the case, it was in fact dirt jamming the action shut that led to the replacement of the Ross .
I have been told, but have not confirmed, that the Schmidt Rubin will not fire if the bolt is not fully locked.
I myself would rather be safe than sorry so the extra whack on the bolt handle.
All that being said, the K- 31 is probably the most accurate general issue rifle ever produced, with fairly mild recoil and results that just make it a joy to shoot.
I would buy one before I would even consider another Mauser.