When Dan Roden escapes into the barn at the end of the film, he is holding only the gun he seizes (having just been brought from jail, he had no weapon). After emptying the gun, he suddenly is seen reloading the weapon and magically now has a gun belt on and a furious gunfight ensues. Where did the gun belt and ammunition come from?
There is no way Virginia mayo's character could hit a man at that distance without properly sighting the rifle. In typical movie fashion, she keeps her face above the rifle's sight-line, which at that distance, usually causes misses by dozens of yards at that distance.
When Roden and his men are chasing Len's group, there are nine riders total. After one is killed in the shoot-out, and Len captures Roden's son, there should be seven left in the group. But only six are shown as they ride away.
When Len takes Ann from the pond and throws her on her horse, she is barefooted. Two seconds later in the next scene she is shown on the horse with her shoes on.
The common response by law enforcement transporting mouthy prisoners, is to gag them to stop their verbally influencing their guards into making mistakes (which this film's plot is predicated on). This would have been just as known to federal marshals then as now.