swift finger-stab at the eyes will make him

let go of your gun. Have the fingers bent a bit, to prevent breakage, do your pushups on fingertips, to build their strength, and shove them THRU his eyeballs, thru the(thin) bone of the occiptal sockets, and STIR his brains with them . He's trying to take your gun so that he can KILL you, so ANYTHING that you do to counter that is justifiable, and QUITE necessary.