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Rimfire ammunition is a type of
firearm A firearm is any type of gun designed to be readily carried and used by an individual. The term is legally defined further in different countries (see Legal definitions). The first firearms originated in 10th-century China, when bamboo tubes ...
metallic cartridge whose
primer Primer may refer to: Arts, entertainment, and media Films * ''Primer'' (film), a 2004 feature film written and directed by Shane Carruth * ''Primer'' (video), a documentary about the funk band Living Colour Literature * Primer (textbook), a te ...
is located within a hollow circumferential rim protruding from the base of its casing. When fired, the gun's firing pin will strike and crush the rim against the edge of the barrel breech, sparking the primer compound within the rim, and in turn ignite the propellant within the case. Invented in 1845, by Louis-Nicolas Flobert, the first rimfire metallic cartridge was the
.22 BB Cap .22 BB Cap (Bulleted Breech Cap) also known as the 6mm Flobert, is a variety of .22 caliber rimfire ammunition. Invented by Louis-Nicolas Flobert in 1845, it was the first rimfire metallic cartridge. The .22 BB Cap and .22 CB Cap are inter ...
(a.k.a. 6mm Flobert) cartridge, which consisted of a percussion cap with a bullet attached to the top. While many other different cartridge priming methods have been tried since the 19th century, only rimfire and the later centerfire cartridges survive to the present day with regular usages. The
.22 Long Rifle The .22 Long Rifle or simply .22 LR or 22 (metric designation: 5.6×15mmR) is a long-established variety of .22 caliber rimfire ammunition originating from the United States. It is used in a wide range of rifles, pistols, revolvers, smo ...
rimfire cartridge, introduced in 1887, is by far the most common
ammunition Ammunition (informally ammo) is the material fired, scattered, dropped, or detonated from any weapon or weapon system. Ammunition is both expendable weapons (e.g., bombs, missiles, grenades, land mines) and the component parts of other we ...
in the world today in terms of units sold.


Characteristics

Rimfire ammunition is so named because the firing pin strikes and crushes the base's rim to ignite the
primer Primer may refer to: Arts, entertainment, and media Films * ''Primer'' (film), a 2004 feature film written and directed by Shane Carruth * ''Primer'' (video), a documentary about the funk band Living Colour Literature * Primer (textbook), a te ...
. 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 other motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the ...
powder 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 i ...
(bullet). Rimfire cartridges are limited to low pressures because the case must be thin enough so that the firing pin can crush the rim and ignite the primer. Rimfire cartridges of .44 caliber up to .56 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, carbon (in the form of charcoal) and potassium nitrate (saltpeter). T ...
was used as a propellant. Modern rimfire cartridges use
smokeless powder Finnish smokeless powderSmokeless powder is a type of propellant used in firearms and artillery that produces less smoke and less fouling when fired compared to gunpowder ("black powder"). The combustion products are mainly gaseous, compared t ...
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) 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 identification, first-in first-out (FIFO), or average cost. ...
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 secondary sector of the economy. The term may refer to a ran ...
is significantly more streamlined than 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 helped lead 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 cartridge consisted of a percussion cap with a bullet attached to the top. These cartridges do not contain any powder, the only
propellant A propellant (or propellent) is a mass that is expelled or expanded in such a way as to create a thrust or other motive force in accordance with Newton's third law of motion, and "propel" a vehicle, projectile, or fluid payload. In vehicles, the ...
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 The .22 CB cap (conical breech cap) is a more powerful version of the .22 BB cap (aka: 6mm Flobert) rimfire metallic cartridge, which was invented by Louis-Nicolas Flobert in 1845. The .22 BB cap and .22 CB cap are interchangeable and are relat ...
(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 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 firearm manufacturer headquartered in Springfield, Massachusetts, United States. Smith & Wesson was founded by Horace Smith and Daniel B. Wesson as the "Smith & Wesson Revolver Company" in 1856 ...
's first revolver, in 1857; it used a longer rimfire case and 4 grains (260 mg) of
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, carbon (in the form of charcoal) and potassium nitrate (saltpeter). T ...
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 5 grains (320 mg) of black powder. This was followed by the .22 Extra Long in 1880, with a case longer than the .22 Long and a heavier bullet. 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 22 Long is a variety of 22 caliber (5.6 mm) rimfire ammunition. The 22 Long is the second-oldest of the surviving rimfire cartridges, dating back to 1871, when it was loaded with a 29 grain (1.9 g) bullet and 5 grains (0.32 g) of black po ...
with the bullet of the
.22 Extra Long The .22 Extra Long is a .22 in (5.6 mm) American rimfire rifle and handgun cartridge. Description Introduced around 1880, the .22 Extra Long was used in Remington, Ballard, Wesson, Stevens, and later (1916) models of Winchester's M19 ...
, giving it a longer overall length, a higher muzzle velocity, and superior performance as a hunting and target round, rendering both the .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, and has a narrower "heel" portion that fits in the case. It is one of the few cartridges that are accepted by a large variety of rifles and handguns. Larger rimfire calibers were used during the
American Civil War The American Civil War (April 12, 1861 – May 26, 1865; also known by Names of the American Civil War, other names) was a civil war in the United States. It was fought between the Union (American Civil War), Union ("the North") and t ...
in the Henry repeating rifle, the
Spencer repeating rifle The Spencer repeating rifles and carbines were 19th-century American lever-action firearms invented by Christopher Spencer. The Spencer was the world's first military metallic-cartridge repeating rifle, and over 200,000 examples were manufactur ...
, the
Ballard Rifle The Ballard Rifle was a single shot, breechloading longarm used during the late American Civil War by Kentucky volunteers. History The Ballard Rifle was designed and patented by Charles H. Ballard in November 1861 in Worcester, Massachusett ...
, and the
Frank Wesson carbine Frank Wesson rifles were a series of single-shot rifles manufactured between 1859 and 1888 in Worcester, Massachusetts. They were purchased by many state governments during the American Civil War, including Illinois, Indiana, Kansas, Kentucky, ...
. While larger rimfire calibers were made, such as the .30 rimfire,
.32 rimfire The term .32 rimfire refers to a family of cartridges which were chambered in revolvers and rifles in the late 19th and early 20th centuries. These rounds were made primarily in short and long lengths, but extra short, long rifle and extra long ...
,
.38 rimfire .38 rimfire cartridges are a type of ammunition that have been in service in the United States since the mid-nineteenth century. The cartridges are produced in short, long and extra long variants. Much like the smaller .32 rimfire, the roun ...
.41 Short The .41 Rimfire Cartridge was first introduced by the National Arms Company in 1863 and was also known as the .41 Short and the .41-100. In most designations like this, the second number refers to the black powder load, though in this case it m ...
(for the
Remington Model 95 The Remington Model 95 is a double-barrel pocket pistol commonly recognized as a Derringer. The design was little changed during a production run of nearly 70 years through several financial reorganizations of the manufacturer causing repeating ...
derringer), the
.44 Henry The .44 Henry, also known as the .44 Rimfire, the .44 Long Rimfire, or the 11x23mmR (11x23mm Rimmed) in Europe, is a rimfire rifle and handgun cartridge featuring a -long brass or copper case. The round has a total overall length of , with a ...
(for the Henry rifle and later used by the famous
Winchester Model 1866 Winchester rifle is a comprehensive term describing a series of lever action repeating rifles manufactured by the Winchester Repeating Arms Company. Developed from the 1860 Henry rifle, Winchester rifles were among the earliest repeaters. The Mo ...
), the
.56-56 Spencer The .56-56 Spencer was an American black powder rifle cartridge. Designed for the Spencer rifle and carbine, patented 6 March 1860, it was employed by cavalry during the American Civil War, first appearing at Sharpsburg in rifle form. No S ...
(for the Spencer rifle was the world's first military metallic cartridge repeating rifle), up to the .58 Miller, the larger calibers were quickly replaced by centerfire versions, and today the .22 caliber rimfires are all that survive of these early rimfire cartridges. The early 21st century has seen a revival in .17 caliber (4.5 mm) rimfire cartridges. New and increasingly popular, the
17 HMR .17 Hornady Magnum Rimfire, commonly known as the .17 HMR, is a rimfire rifle cartridge developed by Hornady in 2002. It was developed by necking down a .22 Magnum case to take a .17 caliber (4.5 mm) projectile. Commonly loaded with a 17 g ...
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 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 o ...
). 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 nail-gun necked down to accommodate a .17 caliber bullet, resulting in substantially 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 1/15th ounce). This " snake shot" 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 10 feet (3.1 m), which is about the maximum effective range, the pattern is about 8 inches (20 cm) in diameter from a standard rifle. Special smoothbore shotguns, such as the ''
Marlin Model 25MG The Marlin Model 25MG is a smooth bore, bolt-action, .22 WMR rifle manufactured by Marlin firearms Company. It was designed to shoot snake shot and marketed as a " Garden Gun" for use in dispatching small garden and farm pests. It also has been ...
"Garden Gun"'' can produce effective patterns out to 15 or 20 yards using .22 WMR shotshells, which hold 1/8 oz. 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 9mm 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 9mm Flobert Rimfire among hunters in Europe is the 1.75-inch brass shotshell manufactured by Fiocchi in Lecco, Italy, using a .25 oz shot of No. 8 shot with a velocity of 600 fps.


Common rimfire ammunition

Below is a list of the most common current production rimfire ammunition: *
.17 Hornady Magnum Rimfire .17 Hornady Magnum Rimfire, commonly known as the .17 HMR, is a rimfire rifle cartridge developed by Hornady in 2002. It was developed by necking down a .22 Magnum case to take a .17 caliber (4.5 mm) projectile. Commonly loaded with a 17 ...
(.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 Stinger case *
.17 Winchester Super Magnum .17 Winchester Super Magnum, is a rimfire rifle cartridge developed by the ammunition company Winchester in 2012. It descended from the .27 caliber nail-gun blank by necking down the blank case to take a .17 caliber In guns, particu ...
(.17 WSM) a .17 caliber cartridge based on a modified .27 caliber
nail gun A nail gun, nailgun or nailer is a form of hammer used to drive nails into wood or other materials. It is usually driven by compressed air (pneumatic), electromagnetism, highly flammable gases such as butane or propane, or, for powder-actuate ...
blank case * 5mm Remington Rimfire Magnum (5mm RFM) a .20 caliber cartridge based on similar dimensions to a .22 WMR case *
.22 BB Cap .22 BB Cap (Bulleted Breech Cap) also known as the 6mm Flobert, is a variety of .22 caliber rimfire ammunition. Invented by Louis-Nicolas Flobert in 1845, it was the first rimfire metallic cartridge. The .22 BB Cap and .22 CB Cap are inter ...
and
.22 CB Cap The .22 CB cap (conical breech cap) is a more powerful version of the .22 BB cap (aka: 6mm Flobert) rimfire metallic cartridge, which was invented by Louis-Nicolas Flobert in 1845. The .22 BB cap and .22 CB cap are interchangeable and are relat ...
also known as 6mm Flobert in Europe *
.22 Short .22 Short is a variety of .22 caliber (5.6 mm) rimfire ammunition. Developed in 1857 for the first Smith & Wesson revolver, the .22 rimfire was the first American metallic cartridge. The original loading was a bullet and of black powd ...
, used 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 suc ...
and Olympic and ISSF 25 m Rapid Fire Pistol competition, until being replaced by .22 Long Rifle in 2005 *
.22 Long 22 Long is a variety of 22 caliber (5.6 mm) rimfire ammunition. The 22 Long is the second-oldest of the surviving rimfire cartridges, dating back to 1871, when it was loaded with a 29 grain (1.9 g) bullet and 5 grains (0.32 g) of black po ...
(obsolete but available) *
.22 Extra Long The .22 Extra Long is a .22 in (5.6 mm) American rimfire rifle and handgun cartridge. Description Introduced around 1880, the .22 Extra Long was used in Remington, Ballard, Wesson, Stevens, and later (1916) models of Winchester's M19 ...
Last manufactured in 1935 it pre-dated but was superseded by the .22 LR. It has a longer case than the .22 LR with the same 40-grain bullet. *
.22 Long Rifle The .22 Long Rifle or simply .22 LR or 22 (metric designation: 5.6×15mmR) is a long-established variety of .22 caliber rimfire ammunition originating from the United States. It is used in a wide range of rifles, pistols, revolvers, smo ...
(.22 LR), the most common cartridge made in the world today * .22 Stinger (a form of .22 Long Rifle with a slightly longer case and the same overall loaded length), its case is the basis for the .17 HM2 *
.22 Winchester Rimfire The .22 Winchester Rimfire (commonly called the .22 WRF) is an American rimfire rifle cartridge. History Introduced in the Winchester M1890 slide rifle, it had a flat-nose slug, and is identical to the .22 Remington Special (which differed o ...
(.22 WRF) AKA .22 Remington Special (obsolete but available) *
.22 Winchester Magnum Rimfire The .22 Winchester Magnum Rimfire, also called .22 WMR, .22 Magnum, .22 WMRF, .22 MRF, or .22 Mag, is a rimfire cartridge. Originally loaded with a bullet weight of delivering velocities in the range from a rifle barrel, .22 WMR is now loaded ...
(.22 WMR) * 9mm Flobert is a common garden gun cartridge or
shotshell A shotgun shell, shotshell or simply shell is a type of rimmed, cylindrical (straight-walled) cartridges used specifically in shotguns, and is typically loaded with numerous small, pellet-like spherical sub- projectiles called shot, fired th ...
used in Europe.


See also

* Heeled bullet *
Cartridge (firearms) A cartridge or a round is a type of pre-assembled firearm ammunition packaging a projectile ( bullet, shot, or slug), a propellant substance (usually either smokeless powder or black powder) and an ignition device (primer) within a metal ...
*
Centerfire ammunition Two rounds of .357 Magnum, a centerfire cartridge; notice the circular primer in the center A centerfire cartridge is a firearm metallic cartridge whose primer is located at the center of the base of its casing (i.e. "case head"). Unlike rim ...
*
List of rimfire cartridges Below is a list of rimfire cartridges, ordered by caliber, small to large. Rimfire ammunition is a type of metallic cartridge whose primer is located within a hollow circumferential rim protruding from the base of its casing. Among the most com ...
*
Primer (firearm) In firearms and artillery, the primer () is the chemical and/or device responsible for initiating the propellant combustion that will push the projectiles out of the gun barrel. In early black powder guns such as muzzleloaders, the primer was esse ...


References


Further reading

* Suydam, Charles R. ''The American Cartridge: An Illustrated Study of the Rimfire Cartridge in the United States''. Alhambra, Calif: Borden Pub, 1986. {{OCLC, 26915839 Ammunition Rimfire cartridges