Obviously a real firearm and not a replica built for shooting blanks only.
My understanding is that there is no such thing as a “replica built for shooting blanks only.” Movie sets use only real firearms loaded with blanks or solid, non-firing casting used by background extras. Am I wrong?
In most westerns, the guns are generally real and are merely firing blanks. The guns of that era need no changes to operate with blanks.
So unless they break it against an Indian stuntman’s head, of throw it into the dirt, it’s almost always real.