I have had occasion to compare the two fore-mentioned Jeffery 'Maharajah' guns, mine in .400x3-inch, the other in .333. In all respects (except chambering and ejection) these two rifles were identical, however the actions were NOT the same size: the breech-face for the .400 being some 5mm WIDER than the .333. This fact was not apparent to the eye, however the micrometer doesn't lie!

Furthermore, the .400 is a very tight squeeze into the .333's oak'n'leather case. How do I know this? I acquired the .333's case for my uncased .400 before the former rifle (with stuffed bores) retired to the NT Police firearm museum.