OK, I'm presuming that what you mean by that is that if there's no recoil of the gun when the trigger is pulled, then any movement of the barrel has to be due to the shooter flinching.

My understanding is that in the sport of skeet shooting, some people use special triggers called "release triggers". Unlike normal triggers, release triggers fire the gun when the trigger mechanism is released. That's supposedly to prevent the pulling of the trigger from causing flinching and subsequent movement of the shot gun barrel. I know that because I import stuff from the USA into Canada fairly frequently, and there was one guy I met at the Canada Border Services Office who was wanting to import a release trigger for competitive skeet shooting, and the border guard was having trouble finding the right B3 classification number for such a thing. I ended up talking to the guy, and he explained to me that it was a special kind of trigger that fired the gun when you released the trigger, not when you pulled it, and that was meant to minimize flinching, and hence improve his shooting accuracy. It was apparantly worth several hundred dollars.