Rimfire ammunition

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Rimfire (firearms)
)
Schematic of a rimfire cartridge and its ignition
Not to be confused with Rim (firearms).

A rim-fire (or rimfire) is a type of

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]

Characteristics

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.

Rimfire ammunition is so named because 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

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

Frenchman

.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 "

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

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
.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

Larger rimfire calibers were used during the

centerfire
cartridges.

The early 21st century has seen a revival in .17 caliber (4.5 mm) rimfire cartridges.

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

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+3⁄4 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

.22 WMR, .17 HM2, and .17 HMR

See also

References

  1. ^ "History of firearms" Archived 22 December 2015 at the Wayback Machine (fireadvantages.com)
  2. ^ "How guns work" Archived 22 December 2015 at the Wayback Machine (fireadvantages.com)
  3. ISBN 978-1-61608-287-1
    . Retrieved 23 July 2020.
  4. ^ Bussard, Michael (2010 )"The Impossible .22 Rimfire", American Rifleman
  5. ^ "History of firearms" Archived 22 December 2015 at the Wayback Machine (fireadvantages.com)
  6. ^ "How guns work" Archived 22 December 2015 at the Wayback Machine (fireadvantages.com)
  7. ^ Shooting section (la section de tir) Archived 10 November 2013 at the Wayback Machine of the official website (in French) of a modern indoor shooting association in Belgium, Les Arquebusier de Visé.
  8. ISBN 978-0-89672-439-6
    . Retrieved 25 January 2012.
  9. ISBN 978-0-89689-455-6
    .
  10. ISBN 978-0-89689-936-0
    . Retrieved 25 January 2012.
  11. ^ "Small Arms Ammunition at the International Exposition Philadelphia, 1876" (PDF). 1972. Archived from the original (PDF) on 25 December 2019. Retrieved 2 December 2019.
  12. ISBN 978-1-58160-122-0
  13. ^
    ISBN 0-87349-605-1
    .
  14. ^ "Hornady's New .17 Mach 2 by Chuck Hawks".

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
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