The most used shotgun today is the 12 gauge. Hunters use this versatile and widely available gauge, as do sport shooters, military and law enforcement. It has existed in its current cartridge configuration since the late 1800's.
Shotgun shell casings were originally full length brass or paper hulls with a brass base. Some were sold loaded, but it was also possible to buy them primed and unloaded. The shooter was then able to load the shell as they desired. Frank Chamberlin patented in 1884 a machine which could load 1,500 shotshells per hour, a remarkable feat at the time. Within ten years, Chamberlin had become a direct competitor with Winchester and the Union Metallic Cartridge Company. This proved, unfortunately, to be the beginning of the end for Chamberlin, as he was competing against his suppliers. They were the producers of the components he needed for manufacturing his own shotgun ammunition. Chamberlin left the ammunition industry by 1900 and focused instead on trapshooting devices.
Shotgun ammo technology grew by leaps and bounds in the first fifty years of the 1900's. Brass hulls were replaced by paper hulls, and smokeless powder - more powerful and cleaner burning - replaced black powder. Remington blazed the trail with new products for shotgunners, including in 1951, the introduction of its Model 870 shotgun. Nine years later, Remington introduced shotgun shells with plastic hulls. The case was more robust and kept the contents of the case dry even in the field. One year later, O.F. Mossberg & Sons introduced their iconic pump shotgun, the Model 500.
Shotgun shells commonly fire shot or slug projectiles. Shot is usually pellets made of lead or steel, but shot loads of tungsten and bismuth are available also. Shot pellet sizes vary between 0.36” (000 Buck) and 0.08” (#9 shot). Shotguns are used to hunt birds from dove to turkey. Some jurisdictions allow hunting with shotguns shooting large pellets for large game including deer.
Shotgun slugs are single solid projectiles designed for hunting large game closer than 100 yards. Slugs work well in hunting because the large size transfers high energy into the target. Some shotgun barrels spin the slug with rifling for added accuracy, while other slugs are wrapped in a sabot which is designed designed to increase range and accuracy of the slug in exchange for projectile weight and energy transfer.
The use of the 12 gauge for self defense is growing again, and specialty ammunition is being produced, including options for low recoil, and combinations of buckshot and smaller pellets. Proficiency with a shotgun for self defense comes more quickly than it does with a handgun, because of the greater inherent accuracy of a long gun. Additionally, 12 gauge shotguns enjoy the advantage of imparting greater energy than a handgun, yet having decreased issues with over penetration.
12 gauge shotgun ammunition will likely remain popular for a long time to come. The 12 gauge is a good choice for many tasks from personal protection to many different types of hunting as there are so many different guns and barrels available.