Brotherhood of the Gun(1991)

After the Civil War, rebel sharpshooter Zack Hollister joins Weir's outlaw gang. After a successful train robbery, he and his brother end up in a gunfight with Weir and his men. He escapes with a wound in his right arm, but his brother is killed. Recuperating he has to learn to shoot left-handed as he plans to avenge his brother's death.