I read an article in a Swedish rifle magazine some time ago. A very good Norwegian long range shooter tested different ammunitions like 6,5x55, .308, .338 and maybe some other. I think he hit targets of 1x1 m regularly with the 6,5x55 and .308 out to 500-700 m, but after that it was more difficult and I think he shot out to 1000-1200 m. And did hit targets of 1x1 m with the .338!