ranges for your cross hairs and circles will be largely decided by the type of ammunition you shoot. you will have to pick a type and go to a range that has targets at several different intervals to find out where exactly your rifle i shooting. youll also want to make sure you have a spotting scope because it would be a pain in the butt to shoot then walk down to the target all the time. my recommendation for your situation is to buy a few different types of ammo and test all of them. Ive never heard of a caliber specific scope that you could just buy and mount. I know the people who made my scope Schmidt & Bender would do a turret job tailored to my rifle and round.