Limp wristing

Limp wristing is a phenomenon commonly encountered by semiautomatic pistol shooters, where the shooter's grip is not firm enough and the wrist is not held firm/straight enough to keep the frame of the firearm from traveling rearward while the bolt or slide of the pistol cycles. This condition often results in a failure to complete the operating cycle, properly termed a malfunction, but commonly (and incorrectly) termed a "jam". Rifles and shotguns, if fired without the stock in the shoulder, may also be prone to limp wristing. Of the important variables involved in this type of jam, bullet and gas momentum, slide and barrel mass, recoil spring pre-load and spring rate, and shooting hand and arm mass are much more important than the compliance (limpness) of the wrist.

The cycling of any type of semiautomatic firearm can be broken down into two phases; the first is the rearward motion of the bolt or slide (hereafter referred to only as slide, which is the most common form in pistols), the second is the forward motion of the slide. The rearward motion of the slide is initiated by the force of firing, and continues using the slide's inertia. While the slide moves rearwards, a spring, called the recoil spring, is compressed, absorbing the energy of the slide while slowing it down. Approximately 50% of the momentum imparted by the bullet and gas is converted into kinetic energy of the slide relative to the frame. This energy is stored by the recoil spring. The other approximate 50% of the momentum is converted to the kinetic energy by accelerating the hand and arm mass. During this phase the fired cartridge case is extracted from the barrel and ejected. When the slide is fully to the rear, it is stopped by the fully compressed recoil spring. The spring then pushes the slide forward, stripping a new cartridge from the magazine and pushing it into the chamber. The firearm is then ready to fire the next round.

Depending on the operating mechanism, there are a number of places that limp wristing can cause a failure to cycle. Recoil operated firearms are more susceptible to failure of this type than blowback and gas-operated firearms, and lightweight polymer framed handguns are more susceptible than heavy, steel-framed or even lighter metal alloy handguns. When there is not enough energy to move the slide back far enough relative to the frame to cycle the action, it is called limp wristing. When there is too much energy in moving the slide back relative to the frame, it is called slide slam.

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Wikipedia