Rimfire ammunition

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

A rim-fire (or rimfire) 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 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 (a.k.a. 6mm Flobert) cartridge, which consisted of a percussion cap with a bullet attached to the top. [1] [2] 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 (5.6mm) or less) and centerfire cartridges have survived to the present day with regular use. The .22 Long 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. [3]

Contents

Characteristics

Comparison of centerfire and rimfire ignition Centerfire & rimfire ignition.gif
Comparison of centerfire and rimfire ignition
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. 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.

Rimfire ammunition is so named because 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 so that the firing pin can 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. [4] 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.

History

6mm Flobert or .22 BB Cap ammo with Container .22 BB with Container.jpg
6mm 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. [5] [6] These cartridges do not contain any powder, the only propellant substance contained in the cartridge is the percussion cap. [7] 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 600 ft/s (183 m/s) to 800 ft/s (244 m/s).

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. [8] [9] [10] 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 4 gr (0.26 g) 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'. [11] This led to the .22 Long in 1871, with the same bullet weight as the short but with a longer case and 5 gr (0.32 g) of black powder. This was followed by the .22 Extra Long in 1880, with a longer case and heavier bullet than the .22 Long.

.41 Swiss rimfire cartridge Vetterlipatrone.JPG
.41 Swiss rimfire cartridge
.22 Long Rifle - subsonic hollow point (left), standard velocity (center), hyper-velocity "Stinger" hollow point (right) .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. [12] It combined the casing of the .22 Long with the 40-grain (2.6 g) 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 rimfire cartridge 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. [13] 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 shells

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

Some .22 caliber rimfire cartridges are loaded with a small amount of No. 11 or No. 12 shot (about .067 oz (1.9 g)). 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 ft (3.0 m), which is about the maximum effective range, the pattern is about 8 in (200 mm) in diameter from a standard rifle. Special smoothbore shotguns, such as the Marlin Model 25MG "Garden Gun" can produce effective patterns out to 15 to 20 yd (14 to 18 m) using .22 WMR shotshells, which hold .125 oz (3.5 g) 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. [13] An example of a rare but modern 9mm Flobert Rimfire among hunters in Europe is the 1+34 in (44 mm) brass shotshell manufactured by Fiocchi in Lecco, Italy, using a .25 oz (7.1 g) shot of No. 8 shot with a velocity of 600 ft/s (180 m/s).[ citation needed ]

List of current production rimfire ammunition

Rimfire ammunition, from left to right, .22 Short, .22 Long Rifle, .22 WMR, .17 HM2, and .17 HMR Rimfire Family 2.jpg
Rimfire ammunition, from left to right, .22 Short, .22 Long Rifle, .22 WMR, .17 HM2, and .17 HMR

See also

Related Research Articles

<span class="mw-page-title-main">Cartridge (firearms)</span> Pre-assembled firearm ammunition consisting of a casing, projectile, propellant, and primer

A cartridge, also known as a round, is a type of pre-assembled firearm ammunition packaging a projectile, a propellant substance and an ignition device (primer) within a metallic, paper, or plastic case that is precisely made to fit within the barrel chamber of a breechloading gun, for convenient transportation and handling during shooting. Although in popular usage the term "bullet" is often used to refer to a complete cartridge, the correct usage only refers to the projectile.

<span class="mw-page-title-main">Table of handgun and rifle cartridges</span> Small arms cartridge data

This is a table of selected pistol/submachine gun and rifle/machine gun cartridges by common name. Data values are the highest found for the cartridge, and might not occur in the same load.

<span class="mw-page-title-main">Centerfire ammunition</span> Type of ammunition that is commonly found in small-, medium-, and large-caliber firearms

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

<span class="mw-page-title-main">.22 CB</span> Rimfire ammunition

The .22 CB cap (Conical Bullet Cap), also known as the 6mm Flobert, is a more powerful version of the .22 BB cap rimfire metallic cartridge, which was invented by Louis-Nicolas Flobert in 1845. The .22 BB cap and .22 CB cap are interchangeable and are relatively quiet, low velocity cartridges, designed for indoor target shooting.

<span class="mw-page-title-main">.22 BB</span> Rifle cartridge

.22 BB 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 interchangeable and are relatively quiet low velocity cartridges, designed for indoor target shooting.

<span class="mw-page-title-main">.22 Hornet</span> Rifle cartridge

The .22 Hornet or 5.6×36mmR Hornet is a varminting, small-game hunting, survival and competition centerfire rifle cartridge commercially introduced in 1930. It is considerably more powerful than the rimfire .22 WMR and the .17 HMR, achieving higher velocity with a bullet twice the weight of the .17 HMR bullet. The Hornet also differs significantly from these in that being a centerfire cartridge makes it reloadable, and thus more versatile. It was the smallest commercially available .22 caliber centerfire cartridge until the introduction of the FN 5.7×28mm.

<span class="mw-page-title-main">.22 Winchester Magnum Rimfire</span> Rimfire cartridge

The .22 Winchester Magnum Rimfire, also known as the .22 WMR, .22 Magnum, .22 WMRF, .22 MRF, or .22 Mag, is a rimfire cartridge. Originally loaded with a bullet weight of 40 grains (2.6 g) delivering velocities in the 2,000 feet per second (610 m/s) range from a rifle barrel, .22 WMR is now loaded with bullet weights ranging from 50 grains (3.2 g) at 1,530 feet per second (470 m/s) to 30 grains (1.9 g) at 2,200 feet per second (670 m/s).

<span class="mw-page-title-main">Wildcat cartridge</span> Custom cartridge for firearms

A wildcat cartridge, often shortened to wildcat, is a custom cartridge for which ammunition and/or firearms are not mass-produced. These cartridges are often created in order to optimize a certain performance characteristic of an existing commercial cartridge, or may merely be intended as novelty items.

<span class="mw-page-title-main">SAKO</span> Finnish firearm manufacturer

SAKO, Limited is a Finnish firearm and ammunition manufacturer located in Riihimäki, Tavastia Proper in southern Finland. It also has owned the Tikka brand of bolt-action rifles since 1983, and is now owned by the Italian firearm holding company Beretta Holding.

<span class="mw-page-title-main">.17 HMR</span> Rifle cartridge

.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 Winchester Magnum Rimfire case to take a .17 caliber (4.5 mm) projectile. Commonly loaded with a 17 grain projectile, it can deliver muzzle velocities in excess of 775 m/s (2,650 ft/s).

<span class="mw-page-title-main">Snake shot</span> Handgun and rifle cartridge loaded with lead shot

Snake shot, rat shot or dust shot, more formally known as shotshell or canister shot by technicality, refers to handgun and rifle cartridges loaded with lead shot canisters instead of bullets, intended for pest control. As the names suggest, the main targets for such ammunition are snakes, rodents, birds, and other pests at very close range.

<span class="mw-page-title-main">.22 caliber</span> Index of articles associated with the same name

.22 caliber, or 5.6 mm, refers to a common firearms bore diameter of 0.22 inch (5.6 mm) in both rimfire and centerfire cartridges.

<span class="mw-page-title-main">5mm Remington Rimfire Magnum</span> Bottlenecked rimfire cartridge introduced by Remington Arms Company

The 5 mm Remington Rimfire Magnum or 5 mm RFM is a bottlenecked rimfire cartridge introduced by Remington Arms Company in 1969. Remington chambered it in a pair of bolt-action rifles, the Model 591 and Model 592, but this ammunition never became very popular, and the rifles were discontinued in 1974. About 52,000 rifles and 30,000 barrels for the T/C Contender pistol were sold during its brief production run. Remington discontinued the cartridge itself in 1982, leaving owners with no source of ammunition.

<span class="mw-page-title-main">6.5mm Creedmoor</span> Centerfire rifle cartridge

The 6.5mm Creedmoor (6.5×48mm), designated 6.5 Creedmoor by SAAMI, 6.5 Creedmoor by the C.I.P. or 6.5 CM or 6.5 CRDMR for short, is a centerfire rifle cartridge introduced by Hornady in 2007. It was developed by Hornady senior ballistics scientist Dave Emary in partnership with Dennis DeMille, the vice-president of product development at Creedmoor Sports, hence the name. The cartridge is a necked-down modification of the .30 Thompson Center.

A gallery gun, Flobert gun, parlor gun or saloon gun is a type of firearm designed for recreational indoor target shooting. These guns were developed in 1845, when French inventor Louis-Nicolas Flobert created the first rimfire metallic cartridge by modifying a percussion cap to hold a small lead bullet. In the 19th century, gallery guns were typically pump-action rifles chambered in .22 Short. Gallery guns are still manufactured, although by the late 20th century, they have been eclipsed by airguns for the purpose of indoor shooting.

In firearms and artillery, the primer is the chemical and/or device responsible for initiating the propellant combustion that will propel the projectiles out of the gun barrel.

<span class="mw-page-title-main">.17 Winchester Super Magnum</span> American rimfire rifle cartridge

.17 Winchester Super Magnum, commonly known as the .17 WSM, is a rimfire rifle cartridge developed by the ammunition company Winchester in 2012. It descended from a .27 caliber nail-gun blank cartridge by necking down the blank case to take a .17 caliber (4.5mm) bullet. Initial loadings were with a 20 grains (1.3 g) bullet, delivering muzzle velocities around 3,000-foot-per-second (910 m/s).

<span class="mw-page-title-main">Louis-Nicolas Flobert</span>

Louis-Nicolas Flobert (1819–1894) was a French inventor. He invented the first metallic rimfire cartridge in 1845. It was a major innovation in firearms ammunition technology, as it was previously delivered as separate bullets and gunpowder, pertaining to muzzle-loading firearms. The rimfire cartridge combined both elements in a single metallic cartridge containing a percussion cap, gunpowder, and a bullet, into a single weatherproofed package or container. Before that, a "cartridge" was simply a pre-measured quantity of gunpowder together with a ball (bullet), in a small cloth bag, which also acted as wadding for the powder charge and ball.

References

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Further reading