Very inaccurate Custer was never a "major general". He was, at most a brigadier general of the "volunteers" during the civil war. At the end of the civil war he was commissioned as a Lt Colonel and sent west to fight in the Indian wars against the Lakota, Cheyenne, and some other tribes. He was vastly outnumbered. The Indian tribes had Winchester repeating rifles, whereas Custers troups had merely single shot trap door Springfield rifles. It's a matter of KNOW YOUR ENEMY! This episode takes, shall I say, poetic liberties with a lot of the facts. Still, it's rather interesting to see how the writers, director, producer take falsehoods and try to make it interesting. If Custer had shot military men without a proper courts martial he would NEVER have been just "suspended" for 1 year without pay. They would have courts martialed him and most likely stood him in front of a wall, given him a blind fold, cigarette, and shot him!
No, it makes for a rather subpar episode. I like Yancey Derringer, don't get me wrong. I wish they had been able to make more than one season, but since it was a "Desilu" production, I can understand why it didn't go further. I read somewhere that whoever was involved wanted more say in the production; maybe more money. That would figure. Ruin a highly rated TV show because you want more and Jock Mahoney and the writers/producers said NO. Go figure.