Rimfire ammunition (also rim-fire) is a type of

metallic cartridge A cartridge, also known as a round, is a type of pre-assembled firearm ammunition packaging a projectile (bullet, shot, or slug), a propellant substance ( smokeless powder, black powder substitute, or black powder) and an ignition device ( pr ...

used in

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 ...

s where the primer is located within a hollow circumferential rim protruding from the base of its casing. When fired, the gun's

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 ...

strikes and crushes the rim against the edge of 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, sparking the primer compound within the rim and igniting the propellant within the case. Invented in 1845 by Louis-Nicolas Flobert, the first rimfire metallic cartridge was the (also known as the 6mm Flobert) cartridge, which consisted of a

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 ...

with a bullet attached to the top. While many other different cartridge priming methods have been tried since the early 19th century, such as teat-fire and

pinfire The pin-fire (or pinfire) is an obsolete type of metallic cartridge used in firearms, where the priming compound is ignited by striking a small pin that protrudes radially from above the base of the cartridge. Invented by Frenchman Casimir ...

, only small caliber rimfire ( .22caliber (5.6mm) or less) cartridges have survived to the present day with regular use. The .22Long Rifle rimfire cartridge, introduced in 1887, is by far the most common

ammunition Ammunition, also known as ammo, is the material fired, scattered, dropped, or detonated from any weapon or weapon system. The term includes both expendable weapons (e.g., bombs, missiles, grenades, land mines), and the component parts of oth ...

found in the world today in terms of units manufactured and sold.

Characteristics

It is named rimfire ammunition as the

strikes and crushes the base's rim to ignite the primer. The rim of such a cartridge is essentially an expanded and flattened end section of the case, and the priming compound is filled from inside into the trough cavity inside the rim. The case is then filled with

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 sealed off by the

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 ...

). Rimfire cartridges are limited to low chamber pressures because the case must be thin enough to allow the firing pin to crush the rim and ignite the primer. Rimfire cartridges of up to .58 caliber were once common when

black powder 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 ...

was used as a propellant. Modern rimfire cartridges use

smokeless powder Finnish smokeless powder Smokeless powder is a type of propellant used in firearms and artillery that produces less smoke and less fouling when fired compared to black powder. Because of their similar use, both the original black powder formula ...

, which generates much higher pressures and tend to be of .22 caliber (5.5 mm) or smaller. This also means that rimfire firearms can be very light and inexpensive, as the

production cost Cost of goods sold (COGS) (also cost of products sold (COPS), or cost of sales) is the carrying value of goods sold during a particular period. Costs are associated with particular goods using one of the several formulas, including specific ident ...

of the case material and powder load are both low, and the

manufacturing process Manufacturing is the creation or production of goods with the help of equipment, labor, machines, tools, and chemical or biological processing or formulation. It is the essence of the secondary sector of the economy. The term may refer to ...

is significantly more streamlined than that for centerfire cartridges (which require more steps in the assembly process). As a result, rimfire cartridges are typically very affordable, primarily because of the inherent cost-efficiency of manufacturing in large lots, which has contributed to the continuing market popularity of these small-caliber cartridges.

History

Frenchman Louis-Nicolas Flobert invented the first rimfire metallic cartridge in 1845. The

6mm Flobert This is a list of firearm cartridges which have bullets of a caliber between and . *''Length'' refers to the cartridge case Case or CASE may refer to: Instances * Instantiation (disambiguation), a realization of a concept, theme, or design * ...

cartridge consisted of a percussion cap with a bullet attached to the top. These cartridges do not contain any powder, the only

substance contained in the cartridge is the percussion cap. In Europe, the .22 BB Cap (introduced in 1845) and the slightly more powerful .22 CB Cap (introduced in 1888) are both called 6mm Flobert and are considered the same cartridge. These cartridges have a relatively low muzzle velocity of around to . Flobert also made what he called " parlor guns" for this cartridge, as these rifles and pistols were designed for

target shooting Shooting sports is a group of competitive and recreational sporting activities involving proficiency tests of accuracy, precision and speed in shooting — the art of using ranged weapons, mainly small arms (firearms and airguns, in forms such ...

in homes with a dedicated shooting parlor or shooting gallery. 6mm Flobert Parlor pistols came into fashion in the mid-19th century; they typically featured heavy barrels. This cartridge was improved upon by Benjamin Houllier in 1846. The next rimfire cartridge was the .22 Short, developed for

Smith & Wesson Smith & Wesson Brands, Inc. (S&W) is an American Firearms manufacturer, firearm manufacturer headquartered in Maryville, Tennessee, United States. Smith & Wesson was founded by Horace Smith (inventor), Horace Smith and Daniel B. Wesson as the ...

's first revolver, in 1857; it used a longer rimfire case and of

to fire a conical bullet. According to Berkeley R. Lewis, a firearms historian, this later Smith & Wesson cartridge was 'essentially the same as Houllier's 1846 patent'. This led to the .22 Long in 1871, with the same bullet weight as the short but with a longer case and of black powder. This was followed by the .22 Extra Long in 1880, with a longer case and heavier bullet than the .22 Long. Vetterlipatrone

American firearms manufacturer J. Stevens Arms & Tool Company introduced the .22 Long Rifle cartridge in 1887.Kokalis, Peter: ''Weapons Tests and Evaluations: The Best of Soldier of Fortune'', page 331. Paladin Press, 2001. It combined the casing of the .22 Long with the bullet of the .22 Extra Long, giving it a longer overall length, a higher muzzle velocity, and superior performance as a hunting and target round, rendering the .22 Short, .22 Long, and .22 Extra Long cartridges obsolete. The .22 LR uses a heeled bullet, which means that the bullet is the same diameter as the case, which has a narrower "heel" portion that fits into the case. It is one of the few cartridges that are manufactured and used in a large variety of rifles and handguns. 44 Henry Flat cartridge

Larger rimfire calibers were used during the

American Civil War The American Civil War (April 12, 1861May 26, 1865; also known by Names of the American Civil War, other names) was a civil war in the United States between the Union (American Civil War), Union ("the North") and the Confederate States of A ...

in the

Henry repeating rifle The Henry repeating rifle is a lever-action tubular magazine rifle. It is famous for having been used at the Battle of the Little Bighorn and having been the basis for the iconic Winchester rifle of the American Wild West. Designed and introduce ...

, the

Spencer repeating rifle The Spencer repeating rifle was a 19th-century American lever-action firearm invented by Christopher Spencer. The Spencer carbine was a shorter and lighter version designed for the cavalry. The Spencer was the world's first military metallic-c ...

, the

Ballard Rifle The Ballard Rifle was a single shot, breechloading longarm used during the American Civil War by Kentucky volunteers. History The Ballard Rifle was designed and patented by Charles H. Ballard in November 1861 in Worcester, Massachusetts. Arou ...

, and the Frank Wesson carbine. While rimfire cartridges larger than .22 caliber existed, such as the .30 rimfire, .32 rimfire, .38 rimfire, .41 Short (for the Remington Model 95 derringer), .44 Henry (for the Henry rifle, later used by the famous Winchester Model 1866), the .56-56 Spencer (for the Spencer rifle was the world's first military metallic cartridge repeating rifle), all the way up to the .58 Miller, they were quickly made obsolete by the newly developed

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. ...

cartridges. The early 21st century has seen a revival in .17 caliber (4.5 mm) rimfire cartridges. New and increasingly popular, the 17 HMR is based on a .22 WMR casing with a smaller formed neck which accepts a .17 bullet. The advantages of the 17 HMR over .22 WMR and other rimfire cartridges are its much flatter trajectory and its highly

frangible A material is said to be frangible if through deformation it tends to break up into fragments, rather than deforming elastically and retaining its cohesion as a single object. Common crackers are examples of frangible materials, while fresh bre ...

hollow point bullets (often manufactured with plastic "ballistic tips" that improve the bullet's

external ballistics External ballistics or exterior ballistics is the part of ballistics that deals with the behavior of a projectile in flight. The projectile may be powered or un-powered, guided or unguided, spin or fin stabilized, flying through an atmosphere or ...

). The .17 HM2 (Hornady Mach 2) is based on the .22 Long Rifle and offers similar performance advantages over its parent cartridge, at a significantly higher cost. While .17 HM2 sells for about four times the cost of .22 Long Rifle ammunition, it is still significantly cheaper than most centerfire ammunition and somewhat cheaper than the .17 HMR. First shown at the 2013 SHOT Show, the .17 WSM uses the blank case from a .27 caliber nail gun that is necked down to accommodate a .17 caliber bullet, resulting in a much higher muzzle velocity and energy than the .17 HMR.

Shot shells

Some .22 caliber rimfire cartridges are loaded with a small amount of No. 11 or No. 12 shot (about ). This "

snake shot Snake shot, rat shot, or dust shot, more formally known as shotshell (a name shared with the shotgun shell) or canister shot, refers to handgun and rifle cartridges loaded with lead shot canisters instead of bullets, intended for pest control ...

" is only marginally effective in close ranges, and is usually used for shooting snakes, rats or other small animals. It is also useful for shooting birds inside storage buildings as it will not penetrate walls or ceilings. At a distance of about , which is about the maximum effective range, the pattern is about in diameter from a standard rifle. Special smoothbore shotguns, such as the '' Marlin Model 25MG garden gun, can produce effective patterns out to using .22 WMR shotshells, which hold of No. 11 or No. 12 shot contained in a plastic capsule. Shotshells will not feed reliably in some magazine-fed firearms, because of the unusual shape of some cartridges that are crimped closed at the case mouth, and the relatively fragile plastic tips of other designs. Shotshells will not produce sufficient power to cycle semiautomatic actions, because, unlike projectile ammunition, nothing forms to the lands and grooves of the barrel to create the pressure necessary to cycle the firearm's action. The 9 mm Flobert is a notable rimfire cartridge that is still in production in Europe and is chambered by the Winchester Model 36 in the 1920s. This cartridge is primarily loaded with a small amount of shot, but can also fire a small ball, and is used in "garden gun", which are miniature shotguns. Its power and range are very limited, making it suitable only for pest control. An example of a rare but modern 9 mm Flobert Rimfire among hunters in Europe is the brass shotshell manufactured by Fiocchi in Lecco, Italy, using a shot of No. 8 shot with a velocity of .

List of current production rimfire ammunition

* .17 Hornady Magnum Rimfire (.17 HMR): a .17 caliber cartridge based on a modified .22 WMR case. * .17 Hornady Mach 2 (.17 HM2): a .17 caliber cartridge based on a modified .22 Long Rifle Stinger case, uncommon but available. * .17 Winchester Super Magnum (.17 WSM): a .17 caliber cartridge based on a modified .27 caliber nail gun

blank Blank or Blanks may refer to: *Blank (archaeology), a thick, shaped stone biface for refining into a stone tool *Blank (cartridge), a type of gun cartridge *Blank (Scrabble), a playing piece in the board game Scrabble *Blank (solution), a solutio ...

cartridge, uncommon but available. * 5mm Remington Rimfire Magnum (5 mm RFM): a .20 caliber rimfire cartridge that is based on the .22 Winchester Magnum Rimfire case, it has greater muzzle energy, longer range, and a flatter trajectory over many of the other rimfire cartridges, uncommon but available. *21 Sharp: a new .21 caliber cartridge based on a modified .22 LR case, uncommon but available. * .22 BB Cap: also known as 6mm Flobert in Europe, uncommon but available. * .22 CB Cap: a slightly longer version of the .22 BB Cap rimfire cartridge, uncommon but available. * .22 Short: an early rimfire cartridge that found worldwide commercial success. It was commonly used for

, including Olympic and ISSF 25 m Rapid Fire Pistol competition shooting, until being replaced by .22 Long Rifle in 2005, uncommon but available. * .22 Long: a longer and slightly more power rimfire cartridge that is based on the .22 Short, uncommon but available. * .22 Long Rifle (.22 LR): The most common rimfire cartridge worldwide. It is chambered in numerous firearms including

rifle A rifle is a long gun, long-barreled firearm designed for accurate shooting and higher stopping power, with a gun barrel, barrel that has a helical or spiralling pattern of grooves (rifling) cut into the bore wall. In keeping with their focus o ...

pistol A pistol is a type of handgun, characterised by a gun barrel, barrel with an integral chamber (firearms), chamber. The word "pistol" derives from the Middle French ''pistolet'' (), meaning a small gun or knife, and first appeared in the Englis ...

revolver A revolver is a repeating handgun with at least one barrel and a revolving cylinder containing multiple chambers (each holding a single cartridge) for firing. Because most revolver models hold six cartridges before needing to be reloaded, ...

s, and

submachine gun A submachine gun (SMG) is a magazine (firearms), magazine-fed automatic firearm, automatic carbine designed to fire handgun cartridges. The term "submachine gun" was coined by John T. Thompson, the inventor of the Thompson submachine gun, to descri ...

s and for various uses including plinking,

hunting Hunting is the Human activity, human practice of seeking, pursuing, capturing, and killing wildlife or feral animals. The most common reasons for humans to hunt are to obtain the animal's body for meat and useful animal products (fur/hide (sk ...

shooting sports Shooting sports is a group of competitive sport, competitive and recreational sporting activities involving proficiency tests of accuracy, precision and speed in shooting — the art of using ranged weapons, mainly small arms (firearms and airg ...

, and

self-defence Self-defense (self-defence primarily in Commonwealth English) is a countermeasure that involves defending the health and well-being of oneself from harm. The use of the right of self-defense as a legal justification for the use of force in tim ...

. * .22 Winchester Magnum Rimfire (.22 WMR): also known as the .22 Magnum, this is a longer rimfire cartridge based on the .22 Winchester Rimfire cartridge with an increase in both muzzle energy and velocity. * .22 Winchester Rimfire (.22 WRF): also known as the .22 Remington Special, it has slightly more muzzle energy than the more common .22 Long Rifle rimfire cartridge, uncommon but available. * .22 Winchester Automatic: also known as the .22 Win Auto, it was only chambered for the

Winchester Model 1903 The Winchester Model 1903 was the first commercially available semi-automatic firearm made by the Winchester Repeating Arms Company. History The Winchester Model 1903 was designed by T.C. Johnson, who had joined Winchester in 1885 and had become ...

semi-automatic rifle A semi-automatic rifle is a type of rifle that fires a single round each time the Trigger (firearms), trigger is pulled while automatically loading the next Cartridge (firearms), cartridge. These rifles were developed Pre-World War II, and w ...

, uncommon but available. * 9mm Flobert: a garden gun cartridge that is still used in Europe, uncommon but available.Fiocchi 9mm rimfire (Flobert). RTP Armor. (n.d.). https://rtparmor.com/products/a_abi9r2-250

Characteristics

History

Shot shells

List of current production rimfire ammunition

See also

References

Further reading