I found an old grave in the middle of a desolate area in Wyoming. I have a nice picture of it.
In the same area of Wyoming I was halfway to the top of a mountain and found and picked up an old .50 caliber brass. Old and well tarnished. I looked up the headstamp and it was manufactured in Saint Louis in 1944. No man would carry a Browning M2 "Ma Deuce" machine gun up that mountain, so my theory is that some Air Force fliers in on a training mission strafed that mountain for target practice. Might have even shot at some elk, since it was a real elky location.
mnmthunting, if you still know where those old boulders are, it would be interesting to go back there with a metal detector and see what other relics you could find in that spot. Possibly some buttons, a buckle, some ammo, some coins, who knows? I think your theory of a dying buffalo hunter is a pretty good one, but it could have been a US Army soldier that got separated from his unit. I don't think a Henry shot a large enough cartridge to make a decent buffalo gun. The US cavalry may have had some Henry's after the Civil War, I know they did not have very many during the Civil war. And Custer certainly did not have Henry's or that whole story may have turned out different.