You can see J.B. mounting Thirty-Thirty up on the wrong side.
BraveStarr is shown going outside a spaceship without a space suit. Space not only has no breathable atmosphere, but also is of 2.7 degrees Kelvin, which is far too cold for any human to withstand.
Marshal BraveStarr removes an armor plate from the outside of a spaceship because it is attracting magnetic asteroids. He does not remove the armor from the rest of the shuttle.