RE: .300 H&H
My dad had one and used it a lot up in Canada. My brother has it now, but doesn't use it much.... he doesn't handload & to buy from the factory is pretty expensive.
The old man would take it up to hunt those big whitetails they have in Northwest Canada..... never heard him complain.
I guess the reason it fell out of favor was the 300 Winchester and 338 winchester.