Dave: I am sure that a fast twist, .40 caliber rifle would make a fine 500 yd gun- maybe even out to 600 yds. However, for 1,000 yds, I think you have to go up to a .45 to be competitive. The small bullet, while lighter, and shooting flatter, is still subject to being pushed around by cross-winds at BP velocities. I think that is why the old Buffalo hunters stayed with the .45 and .50 caliber " Big Bore"( 90-120 grain casings) guns and abandoned the .40 and .44 caliber rifles for their long range shooting, too.
Its almost too bad. I much rather shoot the lighter recoiling .40 calibers, than the .45s, or .50s, over a long afternoon. :thumbsup: