+1 for the Ruger No. 1. As far as caliber, you can't go wrong with a .375 H&H. As for the big calibers, the .375 is one of the more versatile rounds and it easier to find that some of the others. My local Bass Pro (Cincinnati) actually stocks .375.
The No. 1 action is one of the strongest around and the old 45-70 govt can loaded pretty hot. The 45-70 actually can be hot loaded into the lower realms of the .458 Winchester. Might be another round to consider.
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