During my limited amount of training in unarmed combat, the instructor covered attempting to disarm a Bad Guy. The high-speed, flowing sequence is 1. Clear one's body of the line of fire; 2. Control (grab) the BG's weapon; and 3. Attack. (I'd scream as loud as I could, trying for "Psych" as well as action.
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This basically works if you're within maybe five to six feet of the gun; it probably works best if the BG's handgun is in the proto-typical Hollywood extended-arm grip.
It seems pretty well proven that if you make that first move, out of the line of fire, the BG's trigger finger will respond before he turns his body or moves his arm; the first shot misses.
My pesonal opinion is that if I just stood there, I'd likely die; if I do something, I may well be unharmed or "merely" wounded. Howsomever, wounds can be surviveable--and adrenalin helps.
More opinion: Few BGs expect an attack as a response--they learned from both movies or earlier experience. Surprise is always a help.
FWIW,
Art