"Surprise Break" seems like a funny concept to me. I know when the gun is going to go off, more or less. Especially when running something like a 1911, or a revolver in SA mode, you pretty much know when the gun is going to fire. The only time I ever get anything resembling a surprise break, is if I'm slow firing a DA revolver or a DAO pistol. Even then, after enough shooting, your brain pretty much knows when the gun is going off, after you pull the trigger past the "point of no return".
To me, flinching or jerking of the trigger can be a few things-
-subconcious anticipation or "fear" of the gun firing- most of this is the whole "getting used to having a 25,000+ PSI explosion occur right in front
of your face" factor. (not to drift too far, but trying to keep your eyes open while firing, is also part of this- a lot of folks blink during firing, which I would guess plays a role somehow. )
-some subconcious attempt at preemptively controlling recoil- eg, some folks think they have to apply extra muscular effort to attempt to "control"
the gun when it fires instead of just letting it recoil on its own accord.
-simple overapplication of force to the trigger at the desired time. This can be caused by a whole bunch of things- attempting to shoot faster than
your brain/muscles are capable of, "performance anxiety" - eg, letting your fundamentals go to hell because you're trying to make up for what you think is lost time; or even just plain old fatigue - when you get tired, or are tired mentally or physically, people tend to get sloppy. It's easy to slap the hell out of the trigger when fatigued.
I think newbies get hit hardest with the first two, and then the rest of us have problems with the third, which is (mostly) overcome by lots of training and muscle memory type stuff; and some of it is mental conditioning. (Call me crazy, but I find pre-visualization to be a valuable skill- eg, think of what you WANT to happen when performing the course of fire before you start, and your brain might, to some degree, "make it so".
The third one also seems to be caused by going faster than you're actually capable of shooting. Sometimes you have to push this envelope to increase
speed, but you have to balance speed vs accuracy- eg- how long do I let the sights settle vs how quickly should I pull the trigger? A "controlled slap" will work for many shots... of course the success rate is going to vary depending on the shooters acquired skills.
The third factor also gets worse the worse the trigger is. For example, I find discrete control of something like a halfway decent 1911 trigger far
easier to manage than most DA/SA triggers in SA mode (with some limited exceptions). Of course, up to a point, technique can overcome problems with even the crappier triggers. A good shooter can shoot decent even with a mediocre trigger; but once you go into terrible land (like the stock MA M+P trigger) the job gets a LOT harder.
I'm probably all washed up/FOS, but that's how it "feels" to me. I'm no handgunning guru by ANY stretch of the imagination, but this is the kind of
things I've felt when combating flinching and the like. I find dry fire exercises to be extremely valuable, if done right.
-Mike