At some length of barrel, the amount of velocity lost amounts to achieving a velocity that is matched by a smaller more efficient case.
: How much velocity do you have to lose before the High Energy Fed or light Magnum loads by Hornady in the '06 meet or match those of the .300 mag?
: Personally, I see no reson for a magnum barrel length to be less than about 25".
: The magnum rounds should be used as intended, for longer range shooting of hooved animals.
: Generally speaking, one goes to shorter barrels to gain maneuverability in tight hunting locations. In these hunting situations, a long range rifle isn't needed in the first place.
: Dropping the barrel length to 20" on a big case like the .300 Winchester will reduce it's velocity around 210fps or thereabouts, depending on bullet weight. That 200fps is all that separates the .300 from tha afore mentioned factory .30/06.
: If one wants power and a handy rifle for close range shooting out to 200yards, one need only go to something like the .45/70 (or .458) Marlin Guide guns with 18 1/2" to 20" barrels. With them, a 400gr. Barnes, propelled by 49gr. Reloader#7 will make 2,007fps with safe pressure. That's power in a short package, something the .300 WM doens't muster in the same length gun. For interest's sake, add a few inches to that .45/70 barrel and gain another 100fps. Whoopee, not it matches factory ballistics for a famous all-round African big game hunting round.
: I've mellowed in my old age to the point where I do see a place for the small calibre 'magnums' in the hunting arena, but they don't have carbine length barrels.
: I cannot imagine burning 82gr. of powder, just to receive .30/06 ballistics, obtainable with 55gr.
: My vote says that is too short, as is any barrel length in the .300 magnums less than 24" & I'd prefer 25", a nice all-round length. If I need a shorter gun than that for a particualr situation, I've some Winchester 94's and others for that.