The .243 is a nice caliber for longish ranges as there is a wide assortment of fine 6mm bullets that you can use. The choice will be limited by the twist rate of your rifle.
I agree with MM about the 600 yard thing, it was the distance I was going to specify as long as you can hold the waterline for that distance. You notice that MM uses 208Amaxes in his .308 and 30-06; he is trading muzzle velocity for BC and that's critical at longer distances. This will become important for your .243 also since there is quite a range of BC values depending on the bullet selected. BC increases with weight and length (provided the profile is there also.) A higher BC value will help you buck the wind and can somewhat make up for bad wind calls as distances increase.
This is where the twist of your barrel comes into play and if you have a 1:7 or 1:8 twist in the .243 you can use the higher BC bullets. If the twist is slower than that, it may create a problem for you. Just something to keep in mind.
I have a Kestrel 2500 meter and it does a good job telling you the conditions at your location. You still have to figure out what's happening downrange.
