Or- you could build another - this one would fit. Same case for both. The rimmed case is a .348 Winchester, necked up to .45 and taper reduced - same rim diameter as the .45/70.

The one on the right is the same .348 Case, with rim turned down + extractor groove to fit a magnum bolt face (#4 Enfields need no modification to extractor) for function in a bolt actioned rifle. This ctg. also fits Mausers just fine.

Capacity is just a few gr. greater than a .458 Winchester.

I call it the .458 Alaskan.