I had the "privilege" of seeing the real ex-military guy reacting...
You don't get out much do you...?
I'm also a combat veteran, and if startled by perceived gunfire I would react similarly - duck, move, take cover, reach for primary or secondary.... Nothing to do with PTSD (which I do not have). It's training and reaction. Just like a good driver will swerve instinctively to avoid a hazard in the road without any actual thought, just reaction.
Having been very well trained in firearms, and trained countless others, I can say that Max's reaction was totally reasonable for the reasons I've already stated. He made an error in judgment and that can and does happen. Ever watch real gunfights and shootouts... it's not like the movies. People do unexplainable things when they have tunnel vision in life and death situations.
The bigger issue really is the odd scene setup, because it is nearly implausible and borderline impossible. Where are these bikers hiding, considering he just drove past them to get to his position... and that shot with the snub revolver at that range from a seated unsupported position is one of the most unlikely shots in movie history. Given that it is among the most awesome and necessary scenes in the movie, it's a shame the setup was so lousy because the action and results are so awesome. It could have been fixed by building a small shack or other concealment and having them step out with a hunting rifle... simple fix and infinitely more reasonable. Oh well, still and A+ movie for me in spite of that nit-picking.
