00 buckshot

A shotgun shell is a self-contained cartridge typically loaded with multiple metallic "shot", which are small, generally spherical projectiles. The shells consist of a case mounted on a brass base holding a primer. The shot is typically contained in a small container inside the shell casing. Shot has traditionally been made of lead, but steel, tungsten or bismuth is frequently used due to restrictions on lead. A shotgun shell can contain a single, large projectile known as a shotgun slug. They can also be made with specialty non-lethal rounds such as beanbag rounds, and rubber. Shotguns have an effective range of about 45 meters. An old non-lethal round consisted of a shotgun shell loaded with rock salt, which could inflict very painful, but rarely deadly, wounds, and was popular for scaring away trespassers.

Most shotgun shells are designed to be fired from a smoothbore barrel, but dedicated shotguns with rifled barrels are limited to sabot slugs. A rifled barrel will increase the accuracy of sabot slugs, but makes it unsuitable for firing shot, as it imparts a spin to the shot cup, causing the shot cluster to disperse. A rifled slug uses rifling on the slug itself so it can be used in a smoothbore shotgun.

Early shotgun shells used brass cases, not unlike rifle and pistol cartridge cases of the same era. These brass shotgun hulls or cases closely resembled rifle cartridges, in terms of both the head and primer portions of the shotgun shell, as well as in their dimensions. Card wads, made of felt, leather, and cork, as well as paperboard, were all used at various times. Waterglass was commonly used to cement the top overshot wad into these brass shell casings. No roll crimp or fold crimp was used on these early brass cases, although roll crimps were eventually used by some manufacturers to hold the overshot wad in place securely. The primers on these early shotgun shells were identical to pistol primers of the same diameter.

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Wikipedia