Beginning at the 25:15 mark...
"And then even Tippit's gun was taken away from the scene. There was a witness who was kind of out of control, a former Marine named Ted Callaway, who took Tippit's gun which he [Tippit] fell on top of when he [Tippit] got shot.... So Tippit's gun could have been swapped out for another gun too and that's important because if he shot Kennedy from the grassy knoll maybe they didn't want the actual gun to be anywhere near the evidence at that point."
Is McBride really saying that anyone, Tippit or otherwise, would be using a service revolver in an attempt to shoot the President from roughly one hundred feet away?