I stole this off a website......it details that fateful day in late June 1874 and pretty much mirrors everything I've read previously.
The "group of riders" refers to 15 mounted Indians.
No reason not to believe that William Dixon did indeed make the shot.
"Dixon was a renowned rifle shot. Not only did he employ his marksmanship skills in making a living, but he also practiced the sport of long-range target shooting. Further, he had the best equipment then available and that, I must add, was equipment that would rival some of our best today. Keep in mind that some of the long-range target records set in the 1870s & 1880s stood for generations, e.g., a 1000 yard group measuring 8.6-inches fired in 1886. Dixon was not handicapped by lack of equipment. In competent hands, given a good estimate of range and calm conditions, Dixon’s 50-2½ Sharps was a formidable long-range combination. Unfortunately, we do not know the details of his load. However, almost certainly he used a paper-patched, pointed bullet weighing well over one-ounce. Also he almost certainly handloaded, using the best powder then available and due care in all aspects of cartridge production.
After adjusting his long-range sight, Dixon took careful aim and no doubt made a few fine adjustments for any slight breeze, bullet rotation, alignment of the planets, that itch behind his neck, and any other effects he might have though significant. He then touched the finely adjusted set trigger to loose a projectile. His stated target was “The group of riders.”
If his bullet was the lighter Sharps type (approximately 500 grains) muzzle velocity would have been about 1350 fps. For the (more likely) heavier type (about 700 grains) muzzle velocity would have been about 1100 fps. At 7/8 of a mile the lighter bullet would have delivered about 535 foot pounds of energy; the heavier bullet about 845 foot pounds of energy. 1538 yard time-of-flight is practically identical – about 5.3 seconds.
Meanwhile, if any among the Indians were watching, they might have seen a cloud of smoke in front of Hanrahan’s store. It is easy to imagine their mirth at the thought of some foolish White-Eyes wasting powder and lead. Then, an eternal 4.1 seconds later, if they were quiet, they would have heard the distant rumble of a Big-Fifty Sharps rifle.
About 1.2 seconds later, the impossible happened! One of the assembled chiefs took a bullet and was toppled from his horse – most undignified! Not surprisingly, the remaining chiefs recognized that little incident as bad medicine; they therefore and forthwith terminated the Battle of Adobe Walls.
Masterson claimed and Dixon believed that he had killed the rider. Indian accounts claim the chief survived after a bullet hit him above the elbow and broke his arm. Regardless, the bullet did the intended job."
