Anachronisms: Use of MG42s, a machine gun developed in Germany three decades after the Mexican revolution.
Continuity: The dynamite Sean hands Juan before the bank raid is several sticks in a bundle, with a single fuse and cap in the center, but when Juan dynamites the vault door, he uses two single sticks, individually fused and capped.
Continuity: When Sean sets his machine gun back on its tripod after setting the charges, it is loaded with a section of belt with no more than (possibly) fifty cartridges; he is never seen to reload it, but fires many more shots than that. Also, when he stops shooting, it is because the gun has run out of ammunition - we can clearly see the bitter end of the belt go through the action, leaving empty links hanging on the right side, and no belt at all on the left side. But in later shots there is a belt with unfired cartridges visible on that side - though it seems to change length between shots.
Anachronisms: Although the action takes place circa 1914, when Mallory's possessions are rifled by Miranda's family, a flag with the legend "IRA" is pulled out. The IRA was not formed until 1919.
Anachronisms: In the train, the automatic pistol that Juan Miranda uses is a Browning GP35. As its names suggests, this model has become available in 1935 (so contemporary of the mentioned MG42).
Continuity: When Juan is in the bank, after he lets some of the prisoners go, a soldier appears walking down the stairs in the background.
Continuity: When the deserter is taken from the train to be executed along with two others the wall behind him is shot at and damaged on both sides of the deserter. The following close-up shot of the deserter getting shot in the back reveals no damage to the wall.
Revealing mistakes: When Juan's youngest son is shown lying dead, the actor can be seen breathing.
Revealing mistakes: In the train wreck sequence, some of the miniature shots of the explosion and the train being destroyed were not printed in proper anamorphic format, and are badly distorted.
Anachronisms: A close-on shot of one of the convoy's trucks as it rolls through mud shows a modern pneumatic tire and wheel.
Revealing mistakes: Juan's machine gun is not pointing at Gutierez as he shoots him.