Lawdog
Yes, I agree
muzzle blast would, no doubt, be considerably higher as the barrel was shortened
and, the muzzle velocity losses per inch you quoted are reasonable & generally accepted.
However, since Kloshe specifically asked about the .338 Win. Mag.
and since I worked up a pretty "warm", but accurate hand-load (210 gr. Nosler Partition @ 3020 fps) for my pre-64 Model 70 Alaskan (with its factory-standard 26 barrel) in .338 Win. Mag. and hunted all manner of game with it for close to 40 years, I collected Charlie Sisks test on the caliber as a matter of interest to me.
Naturally, when I saw Kloshes querry, I passed Charlie Sisks actual test results along for Kloshes inspection
Personally, I agree with you
I wouldnt shorten the barrel. Butttttttttt
its Kloshes rifle and if that is what he wants to do, I thought hed probably like to see the ACTUAL muzzle velocity loss as each inch came off the barrel.
Strength & Honor
Ron T.