Notes

A firearm is a mechanical device that uses pressure from a burning powder to force a projectile through and out of a metal tube
Action: The action is the heart of the firearm—the moving parts that load, fire, and eject the shells or cartridges. Several types of actions are used in modern firearms. Muzzleloaders have locks instead of actions.Stock: The stock serves as the handle of the firearm. It can be composed of one or two pieces and is usually made of wood or a synthetic material.Barrel: The barrel is the metal tube that the projectile travels through (bullets travel through the barrels of rifles and handguns; shot travels through the barrel of shotguns).
Modern ammunition varies depending on the type of firearm. Rifles and handguns use a cartridge containing a single projectile (bullet). Shotguns use a shotshell containing either a single slug or a large number of small projectiles (shot or pellets). However, the basic components of cartridges and shotshells are similar.
The basic components of ammunition are the case, primer, powder, and projectile(s). Shotshells have an additional component called wad.
Bullets used in rifle and handgun cartridges come in various designs, sizes, and weights. The bullet usually is made of lead and may have a jacket made of copper, brass, or another metal. Bullets used for hunting game may have soft or hollow points designed to expand (mushroom) upon impact. Bullets used for target shooting usually have solid points that make smaller holes.
Centerfire ammunition is used for rifles, shotguns, and handguns. In this type of ammunition, the primer is located in the center of the casing base. Most centerfire ammunition is reloadable.

Rimfire ammunition has the primer contained in the rim of the ammunition casing. Rimfire ammunition is limited to low-pressure loads. Rimfire cartridges are not reloadable Shotgun shells (shotshells) use a slug or shot as the projectile(s).

A slug is a solid projectile, usually of lead, used for hunting big game with a shotgun.
Shot are multiple pellets fired through a shotgun barrel. Shot size is adaptable to the game being hunted. This type of projectile is used typically to hunt game birds and small game animals.
The shotshells must match exactly the gauge and shell length specified by the manufacturer. This information usually is found on the barrel of the shotgun. Shotguns may be chambered for 2½-inch, 2¾-inch, 3-inch, or 3½-inch shells. This refers to the length of the shell after it has been fired. Never load a shotshell that exceeds the approved shell length stamped on the barrel of your shotgun.
You also must choose the correct type and size of shot for the shotshell. In general, as the size of your target decreases, you should decrease the diameter of the shot you use.

As pellet diameter decreases, more shot can be placed in a standard shotshell.
The smaller the shot "number," the larger the pellet diameter.
Shotshell marked as "magnum" means the shell has more shot or more gunpowder than a regular shell. Magnum and regular shotshells are interchangeable if the correct gauge and shell length are used.
Shot size is adaptable to the game being hunted. As pellet diameter decreases, more shot can be placed in a standard shotshell load. The smaller the shot number, the larger the shot size.
Non-toxic shot is required throughout the U.S. for waterfowl hunting. Studies showed that many waterfowl died each year because of lead poisoning. Lead pellets from traditional shotshells were picked up and digested by waterfowl. The toxic effect spread to other birds, such as the bald eagle, which consumed the poisoned waterfowl. To reduce this problem, conservationists worked with shotshell manufacturers to produce effective alternatives to lead shot—steel, tungsten alloy, or bismuth shot.