The element that has to be understood about magnum rifles, is that they require a stout bullet construction at the range most people hunt typical game. Magnum rifles propel a projectile at speeds that typical lightly constructed bullets will not stand up to at ranges generally inside of 200 yards, and even more in some cases.
A good example of a bullet that will hold up to general use in a magnum rifle is the Nosler Partition, Swift A Frame, Accubond, Interbond, Scirocco etc. They are expensive, and are sometimes picky about shooting well.
Since you handload, you can tailor your velocity to the range, game, and bullet you intend to use, and that's a good thing. But for a magnum rifle, at close range, you are expecting a lot from a standard cup and core bullet if you are shooting full house loads.
Take the 257 Wby for example. It shoots a lazer beam trajectory, and really come into its own between 300 and 400 yards. It's flat trajectory is intended to minimize the error of range estimation at long range. But it has a well established reputation for bullet blow up and inflicting cruel wounds inside of 200 yards. It really needs a bullet like the A frame at shorter ranges.
The 7mm Mag is not quite as bad as that, but at typical hunting range, it too places extreme demands on standard bullets. Shooting paper for best accuracy, not a problem. Shooting game at long range with a rifle and shooter up to the task, again, not a problem. Expecting all around performance for general hunting...Premium bullet required, or long and heavy for caliber so as to take advantage of the increased sectional density for adequate penetration.