Anything shorter than 24" with a .300wm to me is a waste.
A lot of things can effect pressures and velocities. What chamber reamer/spec. was used, bore and groove sizes etc.....
I do know for fact in a standard pressure test barrels if your getting 2800fps or more with a bullet 210gr. and heavier most likely your loads are exceeding normal max. working pressures. You might not see it on the brass or bolt lift etc....but I've seen to much load data on test barrels to know what is and what isn't working.
Normal pressure workings loads the .300wm regardless of bullet weight doesn't stay supersonic past 1400 yards. Again I say normal working pressure loads that the .300wm was designed for. That's not to say you cannot hit stuff accurately pass that distance with it though.
Becareful with your loads!
Later, Frank
Bartlein Barrels