I love my Remington 300 ulta mag.It may have the capability of that range butI do not. Your asking what caliber to 600 yards, but 600 yards shots are not easy with any gun.I shoot more than the average Joe and there's no way I would take a shot at 600 yards at any animal. A good gun, a great scope, a good teacher, and hours of practice are what is needed before you should be thinking of 600 yard shots. A Remington 300ultra mag in a 150 grain SwiftScirocco will drop a little over 25 inches at 500 yards. It takes a lot of practice and good equipment to make that shot. JMHO