Hunting mostly but also for long range target shooting.
If you're not shooting at >300 yards on a regular basis, I don't think you'll realize any of the .300 Win Mag's advantages.
Also, you can develop a flinch with heavy recoiling rifles, its not good for accuracy and it's hard to get over itI don't shot long range rifle competition. But I learned from talking to someone who does a couple of months ago that they shun heavy recoiling rifles. After a string of fifty with heavy recoil the accuracy begins to suffer from the human factor. They prefer 223 chambered bolt actions from what I was told.
Dave
If You lived out west and 1000 yd ranges where the norm and long long range hunting shots could be possible, hell try the .300 Win Mag, here in the Gulfsouth, 600 yd ranges are more common and shorter range hunting shots are the norm. I love shooting, reloading, and competiting with my .308