I noticed one weapons flaw ---
There were more than one and most have been noted BUT
The Carbine the Cavalry were using looked a lot like a Trapdoor Springfield
Was not issued until 1876
The Spencer was the cavalry carbine by the time of this raid
7 shot tubular magazine
Had Custer's troops been using the Spencer they may have made it The Springfield of the day would jam after 3-4 rounds The copper shell would swell in the heat