Let's talk about the most plausible situations where you are going to have a gun shoved in your face. Most likely, it would occur during a robbery. If someone was intent on killing you out right, they probably won't wait till they are within contact range if they have a firearm. There are going to be all kinds of variables to consider such as:
Your gut feeling: While there is no way to know for certain, does this appear to be a simple robbery or has the robber given you a feeling that you are going to get shot even if you comply. I believe most of us here would give up any material possession if it meant we wouldn't be shot.
Body language that your assailant is giving off: Do they appear to be nervous (twitchy) or are they experienced criminals. Are they on drugs or impaired? How are they holding the weapon? Do they have their arm out making it easier to push the gun away or is it more in a retention position?
Size and perceived strength of your assailant: Do you even have a chance of wrestling a gun away from them or do they appear to be way stronger or faster?
The presence of possible accomplices: If there are other unsavory characters acting as look outs nearby, going for the assailant's gun may still be a losing proposition, or turn a robbery into a gun fight.
Your actual physical capabilities and training: Are you fairly quick or strong enough to inflict enough damage to your assailant? Do you have any training and how proficient are you?
The presence and location of bystanders: If I have my family with me and there is is a risk that sweeping the gun will cause one of them to get shot, going for the assailant's gun would be an absolute last resort.
The size and type of weapon: Are they carrying a 9mm or better. If not, laugh at them and insult their intelligence, then pull your large caliber handgun and go all Dirty Harry on them. (just kidding). Is it a revolver or semi-auto? Does the assailant have the hammer cocked back?
There could be many more variables that come into play in this situation. If you really feel you are going to get shot regardless, fight for your life. If you have a fairly good chance of taking control of the situation (all conditions seem to be in your favor), that becomes a personal call. There are no guarantees that a robber won't shoot you after you've complied so take their threat of deadly force seriously.
If you decide to act, you need to avoid telegraphing your intentions and try to distract your assailant. I'm not sure how many of us have been at gun point, but you should probably be at least somewhat nervous (unless they are holding a mouse gun
). Get your hands up where it will be easier to grab the weapon. Toss or drop your wallet so they have to move to get it. Look behind them suddenly. It is instinctive for people to look in the direction you look. Move your body out of the way in addition to redirecting the gun. I'm sure there are other tactics so feel free to share them with us.