The Rigby is a MASSIVE case and the .416 Rem is not. the Rem is a higher pressure, high intensity cartridge and handloading can only go so far until case capacity runs out and pressures become unsafe. The big Rigby has a huge case capacity and if loaded to similar pressures as the Remington will produce higher velocity given that it is burning buckets full of powder. Mind you, there is a law of diminishing returns where the large helpings of powder won’t produce a linear increase in velocity, but velocities will be higher in the Rigby none the less. Recoil and muzzle blast will also dramatically increase. The .416 Weatherby is a similar beast but the factory takes the liberty of hot rodding the Weatherby.

Factory loads do not full take advantage of the Rigby’s case size, but a handloader certainly can - if you dare hang on to it.

At the end of the day, John is correct when he states that anything over 2100 FPS is pretty serious medicine, so how much does one need? If one wants, then that is fine too.