For whitetail? Are you serious? Why would you want a 7mm or 300 mag for whitetail?
I know dead is dead, but these generate waaaaay too much energy, recoil, cost of ammo is more and if you reload, burn excessive amounts of powder.
If you want to use a 7mm bullet for whitetails, why not use a 7-08, or a .280. Even a 7mm Mauser. In the 30 cal you have the 300 Savage, 308 Win, 30 T/C, and the everlasting 30-06.