Your .505 observation confirms a suspicion from my own experience. I like the .375 and 9.3 because they have sufficient power with recoil gentle enough for true rapid fire; for me anyway. I once considered a .458 but thankfully tried one out first. I quickly determined the recoil was too much for me to shoot as fast as I felt I should be able.
Before long I plan to have a .416 Taylor made up and load it to mimic the .450/400 just to have a bigger bullet I can still shoot quickly.
