Remember, Reno and Benteen had the same weapons, and dug into a proper defensive perimeter held their ground and survived. A few months later at Cedar Creek, Nelson Miles and the 5th infantry drove Sitting Bull and nearly 1000 warriors over 20 miles, with the same weapons. Tactics, tactics, tactics! THe US Army has a long history of blaming weapons for its tactical failures.
In the age of the BP cartridge, most armys stuck with single shot weapons for a variety of reasons, Simplicity, ruggedness, cost effectiveness, fire control, cartridge power. However valid their reasons, among such weapons the M1873 and its derivitives were simple, effective and fast cycling weapons, and are among the easiest of all to fire from a prone or entrenched position.