The film takes place in the 1840s, yet the guns are mostly repeaters which were not in use yet (though a few might have existed). All pistols are clearly revolvers, rifles are repeaters. Yet the Mexican encampment has a storehouse with kegs of powder, and during the shootout there, several people die trying to bring back a keg of black powder as they were running out of ammo, which would have been useless as they needed bullets not powder.