Re: 300 wsm problem
Not sure if your friend still has the empty brass, if he does then Winchester would like to see them. They need to know the number on the endflap of each box, plus no doubt would like to see the cases.
Had the same thing happen, only the temps were really high at the time we blew a few primers in a .300 WSM.
They have a nice thankyou to maker it worth your while if you go to the bother of sending back stuff like you mentioned. They really need those endflap numbers.