One of the mistakes leading to the Little Bighorn massacre was the fact that the brass didn’t want the soldiers wasting ammo with repeaters.
Also, IIRC (see above at "dotage"), US infantry in the Spanish American war were still carrying black powder trap doors. Cavalry, Rough Riders and Buffalo Soldiers, were armed with new, smokeless, 30-40 Krags at Kettle/San Juan hill.
Oh, and Gatling Guns.