For all practical purposes......yes, in that it can be stuffed full of powder like a 460 Weatherby Magnum, or 450 Dakota, to get max velocity, but technically no....
The 460 Weatherby was based off the parent cartridge, the belted 378 Weatherby Magnum which itself had no parent cartridge, as it was an original case/cartridge design by Roy Weatherby in 1953. The 460 Weatherby Magnum (circa 1957) was necked up to accommodate 0.458 bullets, and is a belted case. It has around 141 grains H20 case capacity.
The 450 Rigby is of course, based off the 416 Rigby parent case, is belt-less, and has around 136 grains H20 capacity, so a little shy of the big Weatherby.
But as far as performance go, the 450 Rigby can get close to the Weatherby, but not best it. Why anyone would want to shoot a 500 grain, 0.458 bullet at 2600-2700 fps is beyond me. Pure masochist.......
The 450 Dakota is for all practical purposes, the same as the 450 Rigby, as it to is based off the 416 Rigby case, with the case dimensions varying ever so slightly. However, it is stoked to the rim with powder to drive it's bullets at 2500-2600 fps, and thus way higher pressures, than the standard load of the 450 Rigby (which was the point...low pressure)....That's probably what you're thinking of as far as similarities.
For, me, I think a 500 grain, 0.458 bullet at 2300 fps is plenty enough thank you very much. I am considering switching to a 550 grain, 0.458 bullet at 2100-2200 fps however.........
