Although the film is set in Texas, the opening is a long-shot of the town and the caption reads, "Laredo, Arizona". There is no border town named Laredo in Arizona, and the Rio Grande River does not flow between Arizona and Mexico.
When Fowler returns with his crates of "machine guns", Sherry Bliss tells him she has found a new song that might catch on, "Camptown Races". The problem with this juxtaposition is that Camptown Races was first published in February of 1850 and automatic rifles were not invented until 1911 nor manufactured until 1914 with the Lewis gun.
When Kansas is captured, Chet (who has his left arm in a sling from a bullet injury) escorts Kansas into a shack while Bragg and all of the other gun smugglers ride back to town. In a subsequent scene, Kansas is shown tied to a bed with rope that circles his torso and binds his wrists to bedposts on each side of his body. How did Chet manage to tie up Kansas? He might have been able to do it with one hand, but he would have had to put his gun down and Kansas would certainly have been able to overpower Chet before he could be tied down. (Even if Chet forced Kansas at gunpoint to do some of the tying himself, it does not look like Kansas could have restricted himself so much that he couldn't have lunged at Chet as soon as Chet grabbed the end of the rope.)