I have only read his book on African hunting, and he is (was) the real deal. Went to unhunted areas in Sudan, CAR etc and really strived for good trophies. He shot a 300 Weatherby most of the time, and I remember him shooting a crop raiding bull with what he calls the .300 Super (378 necked down to .30 sound familiar? 30-378??) but I think his biggest elephant was shot with the .378, although I may be wrong.
There is a picture of his trophy room in the book and it is truly amazing. Considering at the time you had to hunt hard for a full room, not just spend a few weeks in an exotics ranch!