Curing the Fatal Flinch
Why is it we can't always shoot as evenly as this picture? Sooner or later, someone will watch you shooting and say those fatal words, "You're flinching!" Or you feel yourself tense up when shooting and see the shots go low. "I'm flinching" you think. "Don't flinch," you tell yourslf, as you see your shots going lower and lower on the target. "Dont' flinch!" echoes in your mind with each shot, and you curse afterward, "I flinched!"
What is a flinch, anyway? It is your body's reaction to an anticipated shock. The shock can be the loud noise of a gun firing. The shock can be the gun's recoil. The shock can be pain you experience when you shoot. Whatever has caused the shock in the past (that past can be in your current shooting ssession, or long, long ago) your body knows it is coming again, and tries to protect you by clenching many muscles involuntarily. This usually results in your hands moving the barrel of your gun downwards and the shots go low. It happens to handgun shooters and long gun shooters.
As a teacher, I've seen it happen to many students. The number one cause, in my experience, is sound, so the first thing I will suggest is maximizing hearing protection with both foam in-the-ear plugs and high quality, well-fitted muffs.
There are two ways recoil can be the cause of flinching. One is what you might expect, the upward motion of the fired gun. The other is any backward motion; if recoil has ever made anyone feel they might be pushed over backward, that's very unpleasant; the cure might be careful attention to a shooting stance that never threatenes one's balance. Mindfulness of trigger control will slow the trigger pull and help to avoid a slapped trigger that pulls shots low.
If a flinch is caused by the pain of shooting, the pain must be cured, by a different grip or stance, a modification to the gun, a different kind of ammunition, or even a different gun. Shooting should not hurt.
There are many other things you can do to help cure a flinch. Ten of them, including the Ayoob Wedge technique, are here in the article It's a Cinch Not to Flinch. Take a look and see what might help you, or a shooter you know who has this problem.