Factual error: As the colonel and his companions ride out of Blackthorne, Texas, they pass Saguaro cacti, which, oddly enough, only grow in the Sonora Desert, a far distance from Texas.
Continuity mistake: When the bad guy winds up to throw the dynamite into the cantina, McNally puts a round through his brisket, and he falls to the ground clutching his belly. He weakly tosses the dynamite, then stumbles back behind the adobe, now clutching his right shoulder.
Factual error: So the Civil War ends, and the colonel heads for Texas. It must have taken close to a decade to arrive there, for when he rides into Blackthorne, Texas, he's packing a Model 1873 Colt, and a Model 1873 Winchester.
Factual error: When the rebs seize the train, they release the flatcar and caboose. However, since they are on a grade, the knuckles wouldn't separate without slacking up on the strain, either by backing the loco, or pushing the flatcar uphill.