Mistook said:
I'd say Adrianne knows this Rifkin guy from high school, and knows that while he is holding the gun, he believes he's won the confrontation, especially since (we can infer) her hands are going up. He doen't realize it's possible for her to disarm him, but the move she uses is one that might be familiar to fans of the martial arts.
One of the things untrained fighters don't realize is that holding a weapon, be it knife, gun, or club, is that having a weapon does NOT make the person a better fighter.
Most untrained fighters believe that once they hold the weapon they have won the fight. Few realise that a highly trained martial artist can disarm an untrained gun wielder from twenty-one foot away. Police know it, which is why, once they have a drawn gun they are ready to shoot if the perp so much as flinches wrong.
Of course it works the other way as well. Untrained fighters facing either a weapon or someone who looks bigger, stronger, or meaner, may suffer psychological defeat when in truth they could have won easily with a quick snap kick to the knee.
On the other hand a lot of martial artists have learned techniques for disarming a gun wielder that do not work in real life. Slamming the back of the hand holding the gun can actually discharge the gun into the defender's chest with little or no escape possible ... Even though the person holding the gun did not intend to shoot.
You have no control over what the reader knows, worse you have know control over what the reader thinks they know: I myself was a brown belt in competition Judo when I came across a guy with a far lower rank than my own who was very difficult to throw. His instructor had taught him to block my hips -- Not my throw. The reason I was not taught this simple thing was my instructor wanted to keep this info as his "edge" against his students, while the other guy's instructor spent less time teaching his students to throw and more time teaching them to not be thrown, "You can always hit, kick, bite, and scratch if you are still standing up" he told his students, "but once you are on the ground there is not much you can do." (BTW students of ground arts, especially Brazilian will chuckle at the last line, because on the ground is where they want to take you.)
You have to include enough detail that the reader can draw their own pictures based on what they believe to be true, never so much detail to contradict what they think they know,
I believe MRU's would create fight scenes that would be believable for most people. If the two combatants were portrayed as competent, but far from expert, it would work for me. People learning fighting skills spend a long time in the "He swings, I duck and hit back, then he blocks and swings again" mentality, it just doesn't work at the pro boxer, pro wrestler, black belt, or championship swordsman level.