Bronko, How could it be different?
Here are SAAMI Specs for a few of the more popular, Notice the similarities in Bore/Groove Diameters?
.45/70 Government .450 Bore/.456 Groove
.450 Marlin .450 Bore/.456 Groove
.458 Lott .450 Bore/.458 Groove
.458 Win Mag .450 Bore/.458 Groove