Think I would be looking at a .300 WSM rather than a .300 win mag. The .300 Short ultra mag even a bit more preferred.
Do you handload? Is barrel life important to you? The more powder you burn the faster goes your throat and accuracy. The SAUM is the most efficient magnum velocity ctg, although some will tout the WSSM case. A SAUM in a Remington Model 7 if you want lightweight and compact would be very fine.
The primo magnum target/tactical rifle these days is, to my mind, the FN-Herstal in .300 wsm. A winchester 70 is comparable, but not made with chrome-lined barrel.
A .30-06 Ackley Improved will deliver velocities approaching magnum levels IF you are using heavy bullets. The .30/284 wildcat will duplicate the .30-06 in a smaller more compact case and in a long action will allow much bullet seating flexibility.
The .300 Win mag has a short neck and the belt which can be overcome by having gunsmith set the barrel forward so headspace is on the neck.
Barrel life of the .30-06 should last into 5000+ rds. Do the AI chamber and your brass will last longer and you get a bit more power. The .284 case has the .35 degree neck which gives the long brass life. In a world where custom dies were not an extra expense, and .284 win brass easy to come by, I think the .30/284 is the ticket. Magnums get their power from mucho powder and if you get barrel life over 1000rds you are doing very well.
The short magnums are as efficient as the traditional jobs. No, they won't duplicate the .30-378 or anything larger if velocity is your only goal. I would study the loading manuals carefully before deciding. May as well get all the benefits you can when you pay your money....