The phrase “once bitten, twice shy” has to do with getting burned in the past and how one is now skittish about moving forward for fear of getting burned again for the same action. It has nothing to do with Great White’s 1989 cover of the 1975 hit from Ian Hunter. It’s about what happens when you don’t listen to your instructor’s directions about the proper gripping of your handgun.
In this case, the getting burned part is being “bitten” by your firearm in one of two ways: “slide bite” or “hammer bite”. These two bite sensations occur on pistols only. Revolver shooters will not experience either of these “bites”.
The gun’s beaver tail is not just a pretty curved feature of your firearm. It serves a very important safety purpose. The proper grip of the handgun is to have the webbing of the shooting hand wrapped tightly against the underside of the beaver tail, and none of the fingers or any other part of the hand above the beaver tail. Why? When the gun is fired and the slide moves backwards very quickly with the recoil, the purpose of the beaver tail is to allow the slide to move backwards unimpeded by keeping all parts of the hand out of the way of that recoiling slide.
But when a shooter places a finger or webbing of their hand ABOVE the beaver tail, doing so does not allow the slide to recoil backwards unimpeded. This forces the slide to slam into that part of the hand above the beaver tail. And because of the gas pressure emitted when the round is fired, the slide always wins. Anything in the way of the slide moving backward will be moved out of the way or injured. This is a concept known as a “Slide Bite”. And it hurts like a mother!
“Hammer bite” is of a similar nature, but can only occur if the gun has an exposed hammer. As previously mentioned, when the gun fires, the slide recoils backwards very quickly. If the gun has an exposed hammer, it will push the hammer backwards very quickly as it re-cocks the hammer for the next shot.
If the shooter has any portion of their hand, usually the webbing of their shooting hand, ABOVE the beaver tail, when that hammer flies backwards, the hammer will pinch the webbing between it and the beaver tail. That pinching will also hurt like a mother!
Instructors can inform shooters about both slide bite and hammer bite until they’re blue in the face. The best teacher is experience. If the shooter gets bitten enough times, eventually the pain will correct this action. The only benefit the shooter has is a souvenir of their bite to take home to their spouse or partner. “Honey, guess what? I got bitten at the range today. Wanna see?”