They never claimed anything of the kind, and they never loaded it that way.

They brought the 458 Win Mag out in 1956, when Kynoch started dropping the loading of NE rounds for double rifles. At that time, they wanted a cartridge that would closely dup the "BALISTICS" of the 450NE 3 1/4" , in a case that would work in a standard bolt action. To come up with the FPE, of the 450NE,and since they couldn't enough speed they had to use a 500 gr bullet, at a lower speed. The problem was, the compacted powder caused problems, after it was stored for a period of time, or shot in very hot climates. The fact is, the case was simply too small to handle the 500 gr bullet effeciently under all field conditions. The 450's FPE was the target, but since they couldn't consistantly get the speed, they had to use the 500 gr bullet to boost the FPE, and it did that with fresh ammo, and in test barrels, at 70 degrees F. Mr. Lott saw right away, that this cartridge was a problem waiting to happen in the African bush. Sense he was going to use a full lingth case, he retained the 500 gr bullet,which was easy to get in the USA, with the result matching, or surpassing the 470NE. The fact is, Winchester should have used the full lingth 375H&H case in their 375H&H mod 70 action, and loaded it with a 480 gr soft and solid, at 2150fps to start with, and there would have never been a problem. Handloaders would have boosted the velocity, and bullet weight anyway, to what LOTT loaded it to. IMO, if Winchester had used the full lingth 375 H&H case and loaded to 2150fps the resulting 458 WIN MAG would have been the most popular cartridge in Africa since 1956, for a bolt rifle! The 458 LOTT's popularity is the proof today!