Well, I'm astounded at the fact that of all the BS and mis-use of the 'Taylor Knock-out' factor on these forums over the years, this is the ONE (and only!) application where it may actually be valid:
The frontal brain shot on elephant, with a bluff-nose solid.

.....yet no-one mentions it!

Taylor stated that "Any rifle which shows a KO value of not less than 50 can safely be relied upon to knock down an elephant IN ANY CIRCUMSTANCES, though it may not stun him. Over 60 values are necessary if he is to be stunned and not temporarily dazed."

This is as good a definition of a 'stopper' as you're ever going to get!

In the original Kynoch loadings, the 375 H&H turns up a KO of 40.1, the 450/400 is 48.6 or 49.1 depending on which cartridge, and the 450NE is 66.3.

The .458 WinMag with hoppdoc's suggested load is 68.7.

All theoretical I know, but its a bit hard to go out today and test this theory on a couple hundred ele. Taylor did!