Splitting hairs here but my reference book shows the 140 gr water for the Weatherby and 132 grs for the Rigby for a whopping 8 gr difference which in a case this size is basically inconsequential. A difference in brass make can make nearly that much difference in internal capacity. As to the stated pressure differences, so what? Those are numbers assigned to each cartridge and the numbers vary from round to round basically depending on their age. As the Rigby has been around for a lot longer than the Weatherby or the Taylor it will show a lower number and you have to remember its original intent; a powerful round working at relatively low pressure. When loaded originally it was probably loaded in the 45K range. The point of all of this that if you are going to stick to printed max pressures from the good old days, compare them to the max pressures of today for modern versions of these rounds, then sure I get your point. But for all intents and purposes the Rigby and the Weatherby are the same round if loaded to the same pressures which the Rigby can safely do. It could depending on many factors either equal, exceed or come up short load for load against the Rigby, it all depends.. But this all started out as the Taylor vs the Rigby to which you must concede, there is a major difference between these two. Max loadings for the Taylor will usually be around 2450 fps or so, while the Rigby can easily reach over 2600 fps for the same bullet. Another case in point would be the old .404 Jeffery. Original specs called for its 400 gr bullet at around 2100 fps, today even as loaded in some factory ammo it exceeds 2400 fps no problem and its a smaller case than the Rigby. Another really good example is the 7x57 Mauser round. As loaded originally it was somewhat anemic by todays standards, but when loaded in modern rifles to modern pressures it becomes a less antiquated looking round. BTW, yes the .416 Weatherby was based on the .378, which was based on....wait for it.....the .416 Rigby! At any rate I think the horse has been beat to death on this. I see the potential of these old rounds, you prefer to see them as they always were, based on original pressures of 100 years ago. So be it.