Remington 7mm Mag is in the family of belted magnums based on 375H&H Magnum.
.264 Winchester Mag, .275H&H Magnum, .300 Winchester Magnum, .300 H&H Magnum, .338 Win Mag, .375H&H Magnum, .416 Remington Magnum, .458 Winchester Magnum.
I think there might be a .35 Remington mag in there as well as some others.
Remington 7mm Magnum uses a magnum length action.
Remington 7mm Mag is pretty flexible. You can get 100gr to 195gr Barnes in .284 caliber. Not sure if the 195gr is manufactured anymore. 139gr-175gr is common factory ammunition. To get much heavier bullets than 7mm Mag, you need to get at least a .338 Win Mag. barrel.
I am loading 120gr Nosler ballistics for varmint at 3400fps. Also can load 175gr at ~2800fps for large animals. Covers a lot of territory.
I was considering moving up to a .338 Lapua, but not sure that my Parker Hale can take it. And I think it would be cheaper to go to the new Ruger in .338 Lapua.
IMHO: Remington 700 action is accurate, but a Winchester Model 70 action is stronger.
When all is said and done, there is a lot more said than done.