The Gatling Gun Teddy uses against the soldiers was not period correct. The guns when fired produced an enormous dark cloud of smoke due to the chemical composition of the gunpowder used at that time.
The maze shaped marking iron should have been left-right flipped to show the correct maze design when branded.
As Teddy is firing the Gatling gun, the ammunition in the magazine does not appear to move.
At 43:57, when the camera is panning over the bodies of the soldiers, one appears to have a modern tread pattern on the bottom of this boots.