Thought I saw this as "confirmed" by Mythbusters as well?
And even though fiction, it was supposed to be the best shooter at the time, not the average shooter, or even a great shooter.
More than 1 shot needed for Rabbits at 25 yards?
As an inexperienced below average shooter here, with less than a year of shooting casually, and 51 year old eyes, the original 1873 Winchester 38-40 I have loaded with BP and cast boolit, can easily hit a squirrel's head at 50 yards with 1 shot, using stock gun with its iron sights (from a sand bag). 1" groups at 50 yards is normal. I would expect an experienced shooter could do that at 100 yards.
My original 1858 Remington new army .44 cap and ball revolver can easily hit 8" targets all day long at 75 feet using BP and cast round balls.
And don't forget the 45-70 trap door, which was accurate enough in late 1800's to hit targets at 600 yards, and had a required minimum expected accuracy of 4" at 100 yards and 11" at 300 yards, way back then. (I hope to test my 1884 Springfield with cast 405gr HB and BP this weekend). A very skilled marksman back in 1879 could hit a standard military target 2500 yards (more than a mile) away.
http://www.freerepublic.com/focus/news/843705/posts Again, this was using old technology, not today's gear.
But the point I was making was not about the shooter, it was about the cast boolits used that were made with the equipment back then was still adequate to get any job done.
With today's much better components, such as molds, boolit design and weight choices, alloys, boolit lube, BHN testers, temperature measurement and control, calipers, pots, gas cheks, scales, flux, simple cleanliness, etc, as well as powder advancements with dozens of choices, it would seem that even many of our rejects would have to shoot as good or better than many of the normal boolits they hand cast 125 years ago.
So if the above poor accuracy of couldn't hit a door at 25 feet, and 3 shots at 25 yards to hit a rabbit, then that confirms how well our boolits are today. With modern guns and powders, our rejects are still probably much better than what they used to win the west.