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Rimfire ammunition

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File:Rim fire.svg
Schematic of a rimfire cartridge and its ignition

Template:Not to be confused with Template:Use dmy dates

Rimfire ammunition (also rim-fire) is a type of metallic cartridge used in firearms where the primer is located within a hollow circumferential rim protruding from the base of its casing. When fired, the gun's firing pin strikes and crushes the rim against the edge of the barrel 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 Template:Nowrap (also known as the 6Template:Nbsmm Flobert) cartridge, which consisted of a percussion cap with a bullet attached to the top.<ref>"History of firearms" Template:Webarchive (fireadvantages.com)</ref><ref>"How guns work" Template:Webarchive (fireadvantages.com)</ref> While many other different cartridge priming methods have been tried since the early 19th century, such as teat-fire and pinfire, only small caliber rimfire ([[.22 caliber|.22Template:Nbscaliber (5.6Template:Nbsmm)]] or less) cartridges have survived to the present day with regular use. The [[.22 Long Rifle|.22Template:NbsLong Rifle]] rimfire cartridge, introduced in 1887, is by far the most common ammunition found in the world today in terms of units manufactured and sold.<ref>Template:Cite book</ref>

CharacteristicsEdit

File:Centerfire & rimfire ignition.gif
Comparison of centerfire and rimfire ignition
File:Fired rimfire and centerfire casings.jpg
Fired rimfire (left) and centerfire cartridges. A rimfire firing pin produces a notch at the edge of the case; a centerfire pin produces a depression in the center of the primer.

It is named rimfire ammunition as the firing pin 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 (gunpowder) and sealed off by the projectile (bullet).

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 was used as a propellant. Modern rimfire cartridges use smokeless powder, which generates much higher pressures and tend to be of .22 caliber (5.5 mm) or smaller.<ref>Bussard, Michael (2010 )"The Impossible .22 Rimfire", American Rifleman</ref> This also means that rimfire firearms can be very light and inexpensive, as the production cost of the case material and powder load are both low, and the manufacturing process 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.

HistoryEdit

File:.22 BB with Container.jpg
6Template:Nbsmm Flobert or .22 BB Cap ammo with Container

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.<ref>"History of firearms" Template:Webarchive (fireadvantages.com)</ref><ref>"How guns work" Template:Webarchive (fireadvantages.com)</ref> These cartridges do not contain any powder, the only propellant substance contained in the cartridge is the percussion cap.<ref>Shooting section (la section de tir) Template:Webarchive of the official website (in French) of a modern indoor shooting association in Belgium, Les Arquebusier de Visé.</ref> 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 Template:Convert to Template:Convert.

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.<ref name="Eckhardt2001">Template:Cite book</ref><ref>Template:Cite book</ref><ref name="BarnesBodinson2009">Template:Cite book</ref> 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's first revolver, in 1857; it used a longer rimfire case and Template:Convert of black powder 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'.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> This led to the .22 Long in 1871, with the same bullet weight as the short but with a longer case and Template:Convert of black powder. This was followed by the .22 Extra Long in 1880, with a longer case and heavier bullet than the .22 Long.

File:Vetterlipatrone.JPG
.41 Swiss rimfire cartridge
File:.22 LR.jpg
.22 Long Rifle – subsonic hollow point (left), standard velocity (center), hyper-velocity "Stinger" hollow point (right)

American firearms manufacturer J. Stevens Arms & Tool Company introduced the .22 Long Rifle cartridge in 1887.<ref name="Kokalis">Kokalis, Peter: Weapons Tests and Evaluations: The Best of Soldier of Fortune, page 331. Paladin Press, 2001. Template:ISBN</ref> It combined the casing of the .22 Long with the Template:Convert 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.

File:44 Henry Flat cartridge.JPG
.44 Henry rimfire cartridge

Larger rimfire calibers were used during the American Civil War in the Henry repeating rifle, the Spencer repeating rifle, the Ballard Rifle, 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 cartridges.

The early 21st century has seen a revival in .17 caliber (4.5 mm) rimfire cartridges.<ref name="cotw10">Template:Cite book</ref> 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 hollow point bullets (often manufactured with plastic "ballistic tips" that improve the bullet's external ballistics). 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 shellsEdit

File:Munit05.jpg
9 mm Flobert shot, 9 mm Flobert shot, .22 Long Rifle shot, .22 Long Rifle, .22 Long Rifle shot, .22 CB Short, and 9 mm Flobert BB cap

Some .22 caliber rimfire cartridges are loaded with a small amount of No. 11 or No. 12 shot (about Template:Convert). 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 Template:Convert, which is about the maximum effective range, the pattern is about Template:Convert in diameter from a standard rifle. Special smoothbore shotguns, such as the Marlin Model 25MG garden gun, can produce effective patterns out to Template:Convert using .22 WMR shotshells, which hold Template:Convert 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.<ref name="cotw10" /> An example of a rare but modern 9 mm Flobert Rimfire among hunters in Europe is the Template:Cvt brass shotshell manufactured by Fiocchi in Lecco, Italy, using a Template:Convert shot of No. 8 shot with a velocity of Template:Convert.Template:Citation needed

List of current production rimfire ammunitionEdit

File:Rimfire Family 2.jpg
Rimfire ammunition, from left to right, .22 Short, .22 Long Rifle, .22 WMR, .17 HM2, and .17 HMR
  • .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.<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref>

See alsoEdit

ReferencesEdit

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Further readingEdit

  • Suydam, Charles R. The American Cartridge: An Illustrated Study of the Rimfire Cartridge in the United States. Alhambra, Calif: Borden Pub, 1986. Template:OCLC
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