A snap cap is a

firearm A firearm is any type of gun that uses an explosive charge and is designed to be readily carried and operated by an individual. The term is legally defined further in different countries (see legal definitions). The first firearms originate ...

accessory device shaped like a standard cartridge/

shotshell 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 ...

but contains no functional components, namely the primer,

propellant A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or another motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicle ...

(

gunpowder Gunpowder, also commonly known as black powder to distinguish it from modern smokeless powder, is the earliest known chemical explosive. It consists of a mixture of sulfur, charcoal (which is mostly carbon), and potassium nitrate, potassium ni ...

) and

projectile A projectile is an object that is propelled by the application of an external force and then moves freely under the influence of gravity and air resistance. Although any objects in motion through space are projectiles, they are commonly found ...

(

bullet A bullet is a kinetic projectile, a component of firearm ammunition that is shot from a gun barrel. They are made of a variety of materials, such as copper, lead, steel, polymer, rubber and even wax; and are made in various shapes and constru ...

slug Slug, or land slug, is a common name for any apparently shell-less Terrestrial mollusc, terrestrial gastropod mollusc. The word ''slug'' is also often used as part of the common name of any gastropod mollusc that has no shell, a very reduced ...

). It serves the same purpose as a

dummy round A dummy round or drill round is a round that is completely inert, i.e., contains no primer, propellant, or explosive charge (filling). It is used to check weapon function, and for crew training. Dummy ammunition is distinct from "practice" am ...

, but different in that a dummy is usually modified from a real cartridge with its propellant and primer removed (but still has the projectile crimped to the casing), while a snap cap has a monolithic outer shell and is specifically designed to be a fake cartridge from the very beginning. The term "snap cap" is a

generic trademark A generic trademark, also known as a genericized trademark or proprietary eponym, is a trademark or brand name that, because of its popularity or significance, has become the generic term for, or synonymous with, a general class of products or ...

of the fake cartridge originally introduced by American firearm accessory

brand A brand is a name, term, design, symbol or any other feature that distinguishes one seller's goods or service from those of other sellers. Brands are used in business, marketing, and advertising for recognition and, importantly, to create and ...

"A-Zoom", and is a

word play Word play or wordplay (also: play-on-words) is a literary technique and a form of wit in which words used become the main subject of the work, primarily for the purpose of intended effect or amusement. Examples of word play include puns, ph ...

percussion cap The percussion cap, percussion primer, or caplock, introduced in the early 1820s, is a type of single-use percussion ignition device for muzzle loader firearm locks enabling them to fire reliably in any weather condition. Its invention gave ...

. It is now used to refer to any accessory product made to perform similar function.

Description

A snap cap is used to ensure that dry-firing firearms of certain designs does not cause stress and impact damage to the

firing pin 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 sprin ...

and/or the

barrel A barrel or cask is a hollow cylindrical container with a bulging center, longer than it is wide. They are traditionally made of wooden stave (wood), staves and bound by wooden or metal hoops. The word vat is often used for large containers ...

breech. Some snap caps contain a false primer that is either spring-buffered, made of rubber or soft polymer, or none at all. The springs or plastic will absorb the impact force from the firing pin during dry-firing, allowing the user to practice trigger pull or safely test the function of the

firearm action In firearms terminology, an action is the functional mechanism of a breechloading firearm that handles (loads, locks, fires, extracts, and ejects) the ammunition cartridges, or the method by which that mechanism works. Actions are technically ...

without damaging its components. Rimfire and a small number of

centerfire Two rounds of .357 Magnum, a centerfire cartridge; notice the circular primer in the center 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. ...

firearms of older design should not be test-fired with the chamber empty, as this can lead to weakening or breakage of the firing pin and increased wear to other components in those firearms. In the instance of a rimfire firearm, dry firing can also cause deformation of the chamber edge due to the firing pin striking it without the cartridge rim in between. For this reason some shooters use a snap cap in an attempt to cushion the firearm's firing pin as it moves forward. Most commercial snap caps have a polymer/rubber false primer to receive the firing pin strikes, which is usually usable for up to 300 to 400 clicks. After that, due to the impact crater on the false primer becoming deepened from the repeated strikes, the firing pin does not touch and transfer its momentum, and the snap cap loses its cushioning effect. Some higher-end snap caps have a spring-dampened false primer that can last much longer, but are also more expensive to make. Some snap caps are made of a soft aluminum coated with paint. Other snap caps are manufactured using traditional brass shell casings and injecting a polymer material, while others are made from a solid piece of plastic, including via

3D printing 3D printing, or additive manufacturing, is the construction of a three-dimensional object from a CAD model or a digital 3D model. It can be done in a variety of processes in which material is deposited, joined or solidified under computer ...

Uses

Function check

Snap caps are used to confirm a firearm is functioning properly without using live ammunition. In the case of some

repeating firearm A repeating firearm or repeater is any firearm (either a handgun or long gun) that is designed for multiple, repeated firings before the gun has to be reloaded with new ammunition. Unlike single-shot firearms, which can only hold and fire a sin ...

s, it can be used to ensure the

magazine A magazine is a periodical literature, periodical publication, print or digital, produced on a regular schedule, that contains any of a variety of subject-oriented textual and visual content (media), content forms. Magazines are generally fin ...

is feeding ammunition properly up the

feed ramp A feed ramp is a basic feature of many Breech-loading weapon, breech loading cartridge firearm designs. It is a tightly machined and polished piece of metal which guides a Cartridge (firearms), cartridge from the top of the Magazine (firearms), ...

and into the chamber.

Dry-fire practice

Snap caps are used for general dry-firing practice. There is some debate as to if dry firing a handgun may cause damage to the firing pin in a modern firearm. Using a snap cap or

eliminates any potential risk of doing so if the snap cap has a solid primer cup. Some snap caps are made without a primer cup, and thus do not address this potential concern.

Malfunction training

Snap caps and action-proving dummy cartridges also work as a training tool to simulate

firearm malfunction A firearm malfunction is the failure of a firearm to operate as intended for causes other than user error. Malfunctions range from temporary and relatively safe situations, such as a casing (ammunition), casing that did not eject, to potentially d ...

s, the same as a dud would. The shooter loads one or more snap caps into the firearm or magazine along with live rounds; when the trigger is pulled with a snap cap in the chamber, a failure to fire occurs. The shooter can then practice clearing the bad round, which generally requires manually cycling the

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of a

semi-automatic pistol A semi-automatic pistol (also called a self-loading pistol, autopistol, or autoloading pistol) is a repeating firearm, repeating handgun that automatically ejects and loads cartridge (firearms), cartridges in its chamber (firearms), chamber afte ...

Trigger control training

As with malfunction training, snap caps are loaded along with live rounds, so that when the trigger is pulled with a snap cap in the chamber, the firearm does not fire. Here, the intent is to observe whether the shooter maintained proper trigger control (that is, did not flinch). This is often referred to as a ball and dummy drill.

References

{{Firearms Ammunition Firearm training