[rlmorel]

General John Sedgwick: “They couldn’t hit an elephant at this distance.”

[Texas Fossil]

Here is a parallel to your quote:

A Boast that Turned to Toast: Billy Dixon, The Shot of the Century, and the Humiliation of White Eagle

http://www.wadeburleson.org/2014/03/a-boast-that-turned-to-toast-billy.html

Comanche Medicine Man named Quenatosavit (”White Eagle”) called his own fate too.

Technical details on Dixon’s shot from a Sharps 50-90 using a paperpatch black powder cartridge. (estimate between 1,000 and 1,500 yards) https://en.wikipedia.org/wiki/Second_Battle_of_Adobe_Walls

“while a post-battle survey by a team of US Army surveyors, under the command of Gen. Nelson A. Miles, measured the distance: 1,538 yards”