I'm not sure of all models but have heard that Mausers are designed for the older, lower pressure type rounds. Why would someone want to pick a Mauser with or rebarrel to a high pressure round is beyond me and basically firting with disaster. 7mm mag, 270, 308 and many others all operate at too high a pressure to work safely in the Mauser actions. They may be real sweet and economical but that's why I wouldn't even consider one. I don't like that kind of surprise but I am hoping the shooter recovers well from his injury.
Now as far as a lawsuit, a 7mm mag is not a factory Mauser is it? It sounds like a choice the shooter made to have built for him. Therefore may be his own fault. I just don't know the whole story so am only guessing. He'll also have a hard time convincing a jury he was using factory rounds if he reloads. All in all not a good situation to be in.