Only your rifle will tell you what kind of powder charge it wants. I have not seem too many that shoot 3 pellets as well as 2 pellets. And 2 pellets is a good strong load. Even out to 200 yards.

Instead worry about what bullet is best for long range. The Shockwave 200 gr mentioned should be a good long range bullet. Barnes makes some great bullets. Lehigh are said to be good long range bullets also. Then you have Scorpions that shoot well for me. Once you get the right bullet with the right powder charge, then practice and practice a little more. Long shots can be made if you put the time, and effort into learning them.