Scenario:
Attacker points pistol at head.
He is holding the weapon in his right hand,right index on trigger,he can hold one hand or two.
The victim parries the weapon with his left hand going from left to right,(Shooters weapon moves right to left across his body).
The victim steps in grabs the weapon in a two handed catch type grip,elbows attacker in the face once weapon is captured, and turns the weapon up from underneath,Barrel up, from floor to attackers center ,or down from above the attackers head down the center.
Most found the turning of the weapon from floor up to center was best.
Now I have done this with airsoft weapons,and depending on the grip of the attacker and the victim the pistol may fire.
Sometimes the attacker instinctively pulls the trigger when the weapon is struck and or grabbed and turned,sometimes the victims grip assists the attacker in pulling the trigger,(pure accident).
I have also done this with several real weapons,unloaded, one was an M-1911 target pistol that had been worked on and had a light trigger pull ,and this weapon clicked off a good percentage of times,then using a Glock,unworked,and it didn't fire as much,nearly not at all.
We do not know the workings of the weapon an attacker has,if worked on,in working order,or not working at all.
One thing that using the technique,training weapons,simms and unloaded real weapons showed was that one could pull off the move and not be shot,which is the most important aspect of the training.