A friend of mine that has since passed away, had a Remington P-17 rebarreled to 375/404 Improved. As I recall there was very little done in modifications fro the change other than opening the bolt face. The action was designed by the Brits for 303 in the P14, I don't know why they insisted on building them large and strong enough for cartridges twice the size of the 303.
My understanding is that this huge action was originally designed around a large sized, prototype military cartridge, (similar in dimensions to the .280 Ross ?) and ballistically quite similar to the way later Remington 7 mm Magnum, semi-famous hunting cartridge of 1962 introduction.
But WW-I broke out before the project reached full fruition.
So, to meet war production demands, that rifle design was hastily chambered in .303, known as Pattern 14 and in .30-06, known as Pattern 17.
In my opinion, it makes a fine choice for cartridges like the .300 H&H, .375 H&H, .404 Jeffery, .416 Rigby and .458 Lott cartridges, in custom built, African dangerous game styled rifles.
Another thing I like about this design is that the "safety catch" blocks the striker plus, is dead silent to operate as well.