I am thinking of building a long range (200-600yds) target/varmint gun in the near future and have narrowed it down to a few calibers (for now at least). The gun will spend about 90% of its time at the range and the other 10% in the field. The main things I am concerned with in no specific order are barrel wear, availablity of "quality" commercial brass, availability of load data, component choices, yada yada. I have it narrowed down to the 6.5/284, 6mm Ackley, 6 Br, or the 243 WSSM. Any thoughts?

6BR for me, good ballistics, good varmint gun, cheap to shoot, damn accurate, good barrel life, capable to 1000 yards if not neccessarily "The" best at that distance. Lapua brass easily available, wide range of bullets. What's not to like.

If you want something similar with just a bit more poke, how about a 6BR improved(dasher?)

If 600 is your max, go with the 6BR with a 1 in 8 twist. Past that the 6.5/284. 6mm Akley is a good ctg but works better from a long action. I would avoid the WSSM cartridges like the Plague!!