Gents:
I'd like to point out that 22 years before Lott's round, James Watts blew out the .375 H&H for his .450 Watts Magnum. That was 1949. Over two decades later Lott used Watts' round and called it his .458 Lott. Being a well known PH and writer he got the credit but 22 years prior James Watts was the true originator. My book on Jim has sold out of its 1200 copies but I will be pleased to forward a photocopy of the chapter on cartridge development to one of you gents to post it here.
Cal
From the research I've done I've come up with a slightly different conclusion.
James Watts did not develop his 450 on the 375 H&H case, he used the belted basic case. This is an important distinction because when the 375 is necked up to .458, the case gets shorter. It's been several years since I've necked up 375 brass to 458 (and I preferred 416 rem mag brass) so I don't recall exactly how much it shortens but as I recall approximately 0.02" At the time Mr Watts developed his round, the belted basic case was reasonably available.
When Mr. Lott developed his wildcat, belted basic brass was no longer reasonably available (from my understanding) and perhaps he had a good stash of 375 H&H brass on hand and wanted a round that could be made from what brass was available in Africa. In order to provide for a consistent case length for necked up 375 brass, he chose to shorten the case to 2.80" from the 2.85" long 450 Watts.
Whether or not he simply wanted to claim a round of his own design to write an article about and conveniently shortened the Watts 0.050" (assuming he was familiar with the round) to claim a unique design can only be left to our speculation. And yes, the 450 Watts will chamber the 458 Lott just as the 458 Lott with chamber the 458 win mag.
Also worth noting is the 458 Express developed in South Africa based upon a 3.00" long locally produced belted case.
