Jeff

Whilst I am only guessing here, I seriously doubt if Holland and Holland are achieving anything like 2500 fps with a 400 grain bullet in the 400 H&H, the round more or less equals the .416 Remington but with the added inconvenience of a .411" bullet.

Users of the .416 Remington report being able to hit 2400 maybe even a little more, but even then I doubt 2500, this is the realm of the proper .416, the Rigby!!

As for the .375, with careful hand-loading 2600 fps can be achieved, possibly a little more, with a 300 grain bullet but in reality is not relly needed, many will say that the 2500 fps with most of the 300 grain bullets is too fast in any event and that penetration can suffer as a result due to too quick a bullet set up.

There are no free lunches, as you seek a higher velocity so too will you push up chamber pressure, a .375 loaded to 2600 fps with safe pressure at 75* air temp may be unsafe at Zambezi temperatures of 100* plus.

Just my opinion mind.