Rat-shot

Rat-shot (or snake shot) is very small lead shot cartridge (typically #12 – 1.3 mm (0.05")) for use in rifled firearms as opposed to more traditional smoothbores such as shotguns. Such a cartridge with a shot load is often called a shot shell. The most common cartridges loaded with rat-shot are the .22 Long Rifle or pistol or revolver cartridges.  Using rat-shot cartridges allows one to convert a handgun or rifle into a small shotgun suitable for short-range use.

Shot shell cartridges known to be available for hand guns include: .22, .38, 9mm, .40 Smith & Wesson, .44 Special, .45 ACP and .45 Colt. The smaller shot typical of .22s is sometimes called "dust shot".

Uses
Rat-shot is generally used for shooting at snakes, rodents, and other small animals at very close range. It is used by farmers in rifles for the control of birds flying inside of barns and sheds, as well as for killing rats, for the simple reason that rat-shot will not damage the metal roof of a barn or the metal sides of a shed, while still being effective against small pests at close distances. Rat-shot is often used in 22 caliber rifles to train new shooters in the use of a shotgun and as a first step in bird dog training for the dog to get used to loud noises.

Rat-shot cartridges are best used in dedicated smoothbore firearms such as Marlin Firearms' Model 25MG Garden Gun, but can still provide suitable patterns of shot from rifled barrels at short ranges. Since smoothbore firearms with barrels under a certain length may be classified as sawed off shotguns, rifled barrels are legally required in some cases. The Thompson Center Arms Contender pistols offered barrels in some calibers, such as .357 Magnum and .44 Magnum, in configurations that contained special straight rifled choke tubes to improve the patterns produced by the rifled barrels when shooting rat-shot cartridges.

Rat-shot is used in some types of frangible ammunition, such as the Glaser Safety Slug. In these bullets, the shot is glued or sintered together inside a thin shell to form a projectile that fragments readily upon impact, reducing penetration and risk of ricochet.

The maximum effective killing range of rat-shot cartridges is limited, typically being less than 10 to 16½ feet (3 to 5 meters). At this distance, it only has a small chance of tearing through a sheet paper target.

Configuration
While some makes of rimfire ratshot cartridges somewhat resemble traditional shotgun shells, with a brass case crimped closed, many other types of rimfire and nearly all centerfire rat-shot cartridges use a hollow plastic capsule, often shaped like a bullet to aid in feeding, which holds the shot. This plastic case shatters during firing, and allows the shot to disperse after it exits the muzzle. There are reports of the plastic casing shattering when being fed from a magazine. Crimped cases do not exhibit this problem but can fail to extract in some semi-automatic guns.