Primer (firearms) in the context of "Birdshot"

A shotgun cartridge, shotshell, or shell is a type of rimmed, cylindrical (straight-walled) ammunition used specifically in shotguns. It is typically loaded with numerous small, spherical sub-projectiles called shot. Shotguns typically use a smoothbore barrel with a tapered constriction at the muzzle to regulate the extent of scattering.

Some cartridges contain a single solid projectile known as a slug (sometimes fired through a rifled slug barrel). The casing usually consists of a paper or plastic tube with a metallic base containing the primer. The shot charge is typically contained by wadding inside the case. The caliber of the cartridge is known as its gauge.

A firing pin or striker is a part of the firing mechanism of a firearm that impacts the primer in the base of a cartridge and causes it to fire. In firearms terminology, a striker is a particular type of firing pin where a compressed spring acts directly on the firing pin to provide the impact force rather than it being struck by a hammer.

The terms may also be used for a component of equipment or a device which has a similar function. Such equipment or devices include: artillery, munitions and pyrotechnics.

An automatic firearm or fully automatic firearm (to avoid confusion with semi-automatic firearms) is a self-loading firearm that continuously chambers and fires rounds when the trigger mechanism is actuated. The action of an automatic firearm is capable of harvesting the excess energy released from a previous discharge to feed a new ammunition round into the chamber, and then igniting the propellant and discharging the projectile (either bullet, shot, or slug) by delivering a hammer or striker impact on the primer.

If both the feeding and ignition procedures are automatically cycled, the weapon will be considered "fully automatic" and will fire continuously as long as the trigger is kept depressed and the ammunition feeding (either from a magazine or a belt) remains available. In contrast, a firearm is considered "semi-automatic" if it only automatically cycles to chamber new rounds (i.e. self-loading), but does not automatically fire off the shot unless the user manually resets (usually by releasing) and re-actuates the trigger, so only one round gets discharged with each individual trigger-pull. A burst-fire firearm is an "in-between" of fully and semi-automatic firearms, firing a brief continuous "burst" of multiple rounds with each trigger-pull, but then will require a manual re-actuation of the trigger to fire another burst.

A center-fire (or centerfire) is a type of metallic cartridge used in firearms, where the primer is located at the center of the base of its casing (i.e. "case head"). Unlike rimfire cartridges, the centerfire primer is typically a separate component seated into a recessed cavity (known as the primer pocket) in the case head and is replaceable by reloading the cartridge.

Centerfire cartridges have supplanted the rimfire cartridge, with the exception of a few small calibers. The majority of today's handguns, rifles, and shotguns use centerfire ammunition, with the exception of some .17 caliber, .20 caliber, and .22 caliber rimfire handgun and rifle cartridges, a few small-bore/gauge shotgun shells (intended mainly for use in pest control), and a handful of antiquated rimfire and pinfire cartridges for various firearm actions.

A wax bullet is a non-lethal projectile made of wax material — often paraffin wax or some mixture of waxes and other substances that produce the desired consistency — that mimics the external ballistics but not the terminal effects of real bullets. Due to the low weight and density, wax bullets are typically used in a primed centerfire cartridge with little to no propellant powders, as often the primer ignition alone can provide all the necessary energy needed to propel the wax bullet out.

Due to the lack of propellants, wax bullet cartridges do not provide enough recoil/blowback energy to cycle self-loading firearms, so they are most commonly used in revolvers and other manually cycled firearms. Specially designed cartridges and conversion kits can be used together to convert semi-/fully automatic firearms into wax bullet guns, used in tactical training for police and military.