Or you can read about the match between the Irish Rifle Team and the US Rifle team, I believe in 1876, at the old Creedmoor rifle range on Long Island. Much of that match was shot at 1000 yards and the US won over the Irish. We fired Sharps and Rolling block cartridge rifles and some of our guys loaded them from the muzzle. Bodine comes to mind. The Irish were shooting Rigby muzzleloaders. If memory serves me correctly, (CRS), we only won because one of the Irish team members put a shot on the wrong target at 1000 yards. A year or so later there was a rematch and we won again, this time with no misplaced shots by the Irish. There are published pictures of the targets and it was pretty darn good shooting.
I read the same article montana refers to and the guy running the equipment said the same thing you did, "can't be done". Needless to say he was surprised.
Billy Dixons shot at Adobe Walls, Texas was a measured 1538 yards. By his own admission it was a scratch shot. Bill Tilghman killed several buffalo at 600 yards and Frank Mayer, shooting a Sharps with a German telescopic sight of the period killed several at 600+ yards. I once made a crow real nervous at 520 yards, lasered, with one of my Shiloh Sharps in 45-70. My friend who was spotting for me said it looked as if I were within a foot of him.
520 grains of lead started off at 1100-1200 fps. goes a long ways!
Vic