Thanks Dr Deer,
but you are going more deeply into the matter than I was. My reference was to the original contention that the rimless version somehow trumped both the 8x68 and 6.5x55, together with the ballistics tables and photo.

Daryl,
your comments got me examining a bunch of old 338WM cases I don't use any more, in case I had overlooked any incipient head separations. Could not find any internal grooves but I did see five necks (mostly nickel-plated) that were giving up after only three or four loadings. So, in my next life I'll get a 35 Whelen or 9.3x62 or not reload at all.

Cheers