Lots of GOOD choices. Some are just better than others. .243 is a good choice as mentioned above. 25-06 will get it done and is also a good choice. I think that the best is the 6.5 choices. Better BC's on the bullets. Great bullet selection. Then you just need to choose the 6.5 that you like the best. Lots of great choices to choose from. 6.5X47 is very mild yet deadly. J.E. Custom had it right on the .260 Rem. The Creedmoor is also a great choice. Lots of people love the 6.5X284. I shoot a 6.5-06 and its a great caliber. To go faster look at the Sherman or the SAUM. Good luck Bruce
The 223 is perfect out to 600 yards. Alls you have to do is shoot heavier bullets. I shoot the 77 grain bullets and they are great. This is a long range websight I think you should be thinking bigger and longer shooting. Get a 300 Norma mag. Extremely versital you can shoot a 100 grain hollow point all the way up to a 240 smk. Should cover all your needs.