The long barrel is necessary if you want to get the extra velocity the magnum rounds offer, the slow burning powders require more barrel to get the velocity up. I would assume you are looking for more velocity by having a 300 magnum, in addition to your 30-06?? I did the same thing. While a 26 inch barrel can be a little clunky, the magnum only shines out past 300 yards in comparison to the 06, thats the nice thing about having both, you can use the shorter barreled 06 in tight situations, walking around, etc., and use the magnum for sitting in a stand for long range shots.
Sincerely,
Garry