My .375 (1955 Manufacture) isn't cross bolted, but instead inside the stock is a metal bar the action sits against. I very regularly shoot it (50 rounds or so a week) and I have no issue with stock splitting. I tend to shoot either factory Winchester 270gr (to keep brass fresh, mainly) or handloads. Nothing radical on the loadings. It is built like a tank in terms of the stock. The grain of it is very straight on it, so that might be attributing somewhat to its longevity, but I would be of the opinion to say that would be a minor attribute.

A couple of weeks ago I was at the Missoula, MT gun show and handled a very beautiful (99%++) .375 Super Grade (built in 1956). That rifle had the correct stock on it, and a nice cross bolt in it. Weither or not the cross bolt was factory, I can not say, but given the rest of the appearance of the rifle, I would assume it was. The box was with it, if that has any indication of why I am inclined to say that it was a factory stock.