I don't think 26" barrels have been standard on most magnums for awhile, unless you are referring to the Weatherby Magnums which do come with standard 26" barrels.
Actually all of the winchester model 70's and browning a-bolts as well as some remingtom 700's do come with 26" barrels when chambered for the standard magnums such as the 7mmremmag and 300winmag.