My only black powder experience was with an off brand Italian 1860 replica sold thru Cabelas back in the early 90s really cheap. It would shoot a foot low at seven yards, so I was somewhat skeptical of the 75 yards distance of the fight. Then, speaking with others I realized that BP revolvers could be more accurate than in my experiences. I recall some magazine effort to shoot a quality Colt replica out to 75-100 yards and it could score hits at those distances.
One thing that has to be taken into account is that while there were apparently many witnesses, there seems to have been only one official account written up. I don’t recall Springfield, MO reporting any records, especially detailed records of the incident. The official account was picked up by someone and spread nation-wide.
Hickock was a Civil War veteran. He supposedly served as a scout and spy. He wouldn’t have been unfamiliar with the capabilities of his revolvers. It goes to say that with the popularity of the 1851 Navy on both sides, Hickock likely would have carried a pair. Hickock also went on to do a lot of scouting for the Army in the years to follow and purportedly had other handguns. My question has always been that since it never appeared that he had a permanent place to lay his head so where did he stash everything when he traveled? After his murder, they found that S&W .32 on him. The Navies were collected and sold off to cover his burial. The ones they say were his might really be them, nor not. Provenance wasn’t a big thing in 1876 frontier America.
75 yards from a BP revolver is an exceptional shot. A 75 foot head shot from a modern centerfire today is something that most who claim to shoot and carry is exceptional, especially when most are challenged to shoot accurately at the seven yards they claim they practice.