While there is little doubt that Patton was an excellent shot, he was a flamboyant leader who carried those guns mainly for show. AFAIK, he never fired either one at an enemy. (Unless the story of his firing at a strafing plane is true. If it is, he apparently did not bring the plane down.).
There is a story that at one point Omar Bradley, who was Patton's boss, was asked by a young reporter why he didn't carry a gun like Patton did. Bradley, according to the story, replied, "Son, at last morning report, I had 1,300,000 men under my command; if they can't stop the Germans, I don't think one lousy pistol is going to do much good."