As to the .416's the Taylor is 'special' in my book. About the same recoil as a .375H&H and better on all larger species of game at reasonable ranges, ie: 300 yards and closer. Even with the older powders, it will do 2,350 to 2,420fps with 400gr. softs and solids and at safe levels for use in Africa.
: I don't really care if the breech pressure is less in a Rigby - 'Great Deal' for it and it's 100gr. + charge of very slow, bouncy pressure powder.
Hagel, Whooters or whomever else used it had no problems with the .338 necked up to hold .416 bullets back in the 60's, and certainly not today with even better 'Extreme' Hodgdon powders.
: The Rigby was developed to deliver those ballistics with cordite - a powder that developed incredible pressure spikes in hot weather and thus the low pressure of the Rigby. These safety guards caused by lousey powder are rather redundant today.