A semiautomatic handgun requires a trigger squeeze for each shot, and loads fresh cartridges into itself from a vertical magazine inserted into a hollow handle grip. The firing pin is held in a free-floating position by a spring. A double-action revolver draws the hammer back when the trigger is squeezed. A single-action revolver must be cocked by hand. There are also shotguns, such as .410s, which express millimeters, but these are usually smaller bores than 20 gauges.
Bullets generally fragment or mushroom upon impact, depending on their hardness.
They are designed for complete penetration, as in military applications. Soft point , also called round nose, bullets have a tip of metal softer than the core which usually produces a mushrooming effect, to put a bigger hole inside the target. Hollow point bullets are designed to fragment into little pieces, thus taking out different parts inside the target. Shot are composed of lead with a small amount of antimony, and regardless of number, have a muzzle velocity of twelve hundred feet per second. A slug is a hollow, elongated piece of metal, which has longer range and more shock power.