As with other classes of ammunition, shotshell ammunition must undergo priming, charging, and insertion of the projectile(s). It must also be firmly crimped and sealed for integrity. The primary difference between shotshell loading and other types of ammunition is the type of loading machinery.
Most modern high-speed shotshell loaders are dial machines. The cases are held in the outer edges of a large horizontal dial and moved through the loading sequence, stopping at successive workstations. The dial is progressively loaded with empty cases at the beginning of the process and ready-to fire cartridges fall out of the dial when the process is finished. Additional equipment may be used to automate the packing process.
Click here to watch a video on shotshell assembly provided by Federal Cartridge Company.