I have had several 7mm's. Several 7mm-08s, several "straight" .284s, a few 7mm Shehanes and several 7mm Rem Mags. For hunting, it is rather difficult to beat a 7mm Rem Mag. However, once you incorporate 600 yard target shooting in there, the benefits evaporate for the 7mm Rem Mag. Under the stress of long shot strings, from a competitive match, the 7mm Rem. Mag. will eat up throats like candy! On the other hand, limiting the competition to 300 / 600 yards does not take a BIG cartridge. Depending on exactly what your quarry is for hunting, a 7mm-08 is about as fine of a 400 yard cartridge as you can get, for most big game. If Elk or Moose are on the table, the other 7mm's would be a better choice. For the 300-600 yard competitions you are espousing, it (7mm-08) would do very well indeed.
The 7mm-08 is easy to load for and very accurate. The .284's and the improved derivatives, will do anything you need, both in hunting and target shooting. Although they have, from time to time, been finicky to get competitive loads developed for! There are a few other thoughts you might want to consider. One is that the .284 and it's derivatives have a .473 bolt-face, the 7mm. Rem. Mag. has a .532 bolt-face. If you have already purchased a .532 bolt, consideration #2 would be to consider a 7 SAUM. It will, for all intents and purposes, do what the 7mm Rem Mag can do ballistically. If you shoot it for competition, and use SLOW powders, it's barrel life is considerably longer than a BIG 7mm. Rem. Mag.
I hope this helps...
The 7mm-08 is easy to load for and very accurate. The .284's and the improved derivatives, will do anything you need, both in hunting and target shooting. Although they have, from time to time, been finicky to get competitive loads developed for! There are a few other thoughts you might want to consider. One is that the .284 and it's derivatives have a .473 bolt-face, the 7mm. Rem. Mag. has a .532 bolt-face. If you have already purchased a .532 bolt, consideration #2 would be to consider a 7 SAUM. It will, for all intents and purposes, do what the 7mm Rem Mag can do ballistically. If you shoot it for competition, and use SLOW powders, it's barrel life is considerably longer than a BIG 7mm. Rem. Mag.
I hope this helps...