RE: .300 H&H
I remember a pre 64 winchester in 300 Holland & Holland that I could have bought once... wish I had. Actually, it had a rep as a powerful and very accurate cartridge. It was a long bottle neck, which I think actually caused it to lose market share. Shorter, zippier 300's came out and I just stopped seeing them around. It would be interesting to hear from some who still use these.
Great cartridge though. If one were to cast aside availability issues, it would be a great hunter IMO.