noticed the .338 win mag is noticeably shorter than the .300 win mag, and it was explained to me that this is to avoid someone using a .300 win mag round in a .338 win mag rifle.
The stated reason for increased case length, combined with an unusually short neck, was to increase case capacity and therefore ballistic potential. While this had merit, performance difference between this and the wildcat 30-338 (338 Winchester Magnum necked to 30-caliber) is quite modest. Motivation for this design can best be understood by recognizing that Norma introduced the 308 Norma Magnum, a standard 30-caliber magnum, in 1960
I think I explained this to you last week in another post but glad Konnari posted the same thing .. Norma got the jump on winchester...A 338 bullet in a 300 winchester case would be a bad idea. Recoil wise there is not a lot of neck to grip a heavy bullet .