I found it interesting, given the rapid fire of the opening sequence of each show, to learn that the gun is tricked out.
In Season 1, Episode 2, "Home Ranch", a couple of thugs pay Lucas and Mark a visit at their just purchased ranch house in North Fork to threaten them on behalf of a neighboring rancher. They relieve McCain of his rifle and one of them drags him around the field by a rope behind a horse. At the end of the drag sequence, the other thug picks up McCain's rifle; when he works the action, the rifle fires automatically.
"Marty, this thing goes off all by its lonesome. I didn't pull the trigger or nuthin'. This thing has a little old fandango that trips the trigger when you slam the lever home." In many subsequent scenes, McCain routinely opens and closes the rifle's action without firing the gun.

