If it's new it should have included a manual that will tell you what kind of projectiles and powder you can use in it. If it isn't new it wouldn't hurt to write Remington and request a copy of the manual.
I'd be extremely surprised if they recommend against using the pellets, though. A different question to ask is whether or not your game laws allow the use of pellets. Here in Colorado they do not.
Others have offered up a sighting of roughly 2 inches high at 100 yards as a good sighting scheme. In my own experience I have come to favor a sighting of 3.5 inches high at 100 yards. This allows for the individual to hold dead-on (directly in the middle of the top and bottom) the animal out to roughly 350 yards.
Magnum calibers such as the 7mm Remington and 300 Winchester will extend this slightly. At 400 yards I hold directly on the backbone of the animal. The drop at this range allows the...