I recommend starting off with winchester white box 175 grain bullets.
I'm assuming it is a 7mm Remington Mag as it is the most common of the 7mm Magnum family. Make sure you know exactly which cartridge it fires, it wouldn't be a good idea to shoot a 7mm Rem Mag out of a 7mm Weatherby Mag chamber.
Anyways it seems you got one heckuva rifle, with just about the best iron sights in existence. Learn to shoot it well and you will scoff at folks who need a scope to stay in the black at 100
Jimro