4.5×26mm MKR

Last updated
4.5mm MKR (synonyms: 4.5mm Interdynamic, 4.5mm Kjellgren)
Comparative image 7.62NATO 5.56NATO and 4.5x26MKR cartridges.jpg
L to R: 7.62×51 NATO, 5.56×45 NATO, 4.5×26MKR.
TypeRifle
Place of originSweden
Service history
In servicePrototypes only.
Production history
Designed1978
ManufacturerInterdynamics AB
No. builtPrototypes only
Specifications
Parent case .22 WMR
Case typeRimfire, tapered, shoulderless bottleneck
Bullet diameter4.63 mm, 22 mm long, cold-rolled copper, boat-tail spitzer.
Neck diameter5.02 mm
Shoulder diameterShoulderless
Base diameter6.48 mm
Rim diameter7.44 mm
Case length26.10 mm
Overall length42 mm overall length
Primer typeRimfire
Filling0.51 grams tubular nitrocellulose powder or 0.57 grams spherical double-base powder
Ballistic performance
Bullet mass/typeVelocityEnergy
1.58 g (24.4 gr) 1,000 m/s (3,270 ft/s790 J (583 ft lbs)
Test barrel length: 640 mm

The 4.5mm MKR, also known as the 4.5mm Interdynamic or 4.5mm Kjellgren, was a Swedish prototype rimfire cartridge developed for the prototype Interdynamics MKR bullpup assault rifle and carbine.

Contents

History

The 4.5mm MKR was designed in 1978 [1] by Interdynamic AB, a Swedish company, around the time of the rise of "micro-caliber" popularity. Firearms companies everywhere were trying to achieve a type of practical, light and cheap ammunition. Micro-caliber (less than 5 mm (0.20 in) in diameter) ammunition makers wished to achieve higher velocities, flatter trajectories, and greater penetration while keeping weight and recoil low as possible to facilitate controllable use in individual automatic weapons.

Design

The 4.5mm MKR was essentially a .22 WMR rimfire case necked down from 5.6 mm (0.22 in) to accept a 4.5 mm (0.18 in) bullet, for use in the Interdynamics MKR rifle and carbine. It was supplied in single-use, 50-round polymer magazines. The cartridge featured a curved taper of its body to aid extraction and a short, shoulderless neck. Its 4.5 mm (0.18 in) caliber boat-tail spitzer bullet was 22 mm (0.87 in) long and made by cold rolling solid copper wire. [1]

The lightweight bullet of 1.58 g (24.4 gr) reportedly achieved a muzzle velocity of about 1,000 m/s (3,300 ft/s) and a muzzle energy of 790 J (580 ft⋅lbf). This claim contrasts sharply with the comparable, more modern .17 HMR which has a muzzle energy of 340 J (250 ft⋅lbf). Due to the combination of a thin-walled rimfire case with a high-pressure powder charge, the cartridge needed good external support so the MKR rifle was designed to use locked breech, gas-operated action with a vertically tilting bolt rather than straight blow back operation. This ensured the bolt only opened once cartridge pressure had reduced to safe levels. The rifle and carbine, which differed only in barrel length, were fired from the open bolt position to prevent cook-off ignition of the thin walled cartridges. Users could select from semi-automatic, three-round burst, or fully automatic modes. [2] The burst and fully automatic modes had a high rate of fire of 1800 rounds per minute. [1]

Performance

The 4.5×26 MKR was claimed to be on par with a 5.56×45mm NATO M-193 bullet at up to 300 m (980 ft), while one could carry 3.5 times as many of the lighter weight cartridges. Its slender 4.5 mm (0.18 in) projectile could penetrate a steel helmet up to 300 m (980 ft), out to that range it had a similar ballistic curve to the 5.56×45 NATO with M-193 projectile. This was due to a combination of slightly higher velocity, a similar Ingalls ballistic coefficient to the M-193 bullet (0.245 vs 0.265), and the superior penetrating ability of solid cold-rolled copper bullets vs jacketed lead bullets given an equal sectional density. It was potentially lethal at up to 750 m (2,460 ft) with 80 J (59 ft⋅lbf) and its tendency to tumble on impact was twice that of the 5.56 M-193 bullet, thus ensuring more effective transfer of its diminutive energy to its target, especially as its tip tended to bend. Maximum range was 2,500 m (8,200 ft). [3]

Due to concerns about stopping power, reliability, and the inherent problems with using rimfire ammunition, the MKR project was abandoned at the prototype stage and the 4.5mm MKR never saw service or any kind of widespread use. [2]

See also

Related Research Articles

<span class="mw-page-title-main">5.56×45mm NATO</span> Service rifle cartridge

The 5.56×45mm NATO is a rimless bottlenecked intermediate cartridge family developed in the late 1970s in Belgium by FN Herstal. It consists of the SS109, L110, and SS111 cartridges. On 28 October 1980, under STANAG 4172, it was standardized as the second standard service rifle cartridge for NATO forces as well as many non-NATO countries. Though they are not entirely identical, the 5.56×45mm NATO cartridge family was derived from and is dimensionally similar to the .223 Remington cartridge designed by Remington Arms in the early 1960s.

<span class="mw-page-title-main">Caliber</span> Internal diameter of the barrel of a gun

In guns, particularly firearms, but not artillery, where a different definition may apply, caliber is the specified nominal internal diameter of the gun barrel bore – regardless of how or where the bore is measured and whether the finished bore matches that specification. It is measured in inches or in millimeters. In the United States it is expressed in hundredths of an inch; in the United Kingdom in thousandths; and elsewhere in millimeters. For example, a US "45 caliber" firearm has a barrel diameter of roughly 0.45 inches (11 mm). Barrel diameters can also be expressed using metric dimensions. For example, a "9 mm pistol" has a barrel diameter of about 9 millimeters. Since metric and US customary units do not convert evenly at this scale, metric conversions of caliber measured in decimal inches are typically approximations of the precise specifications in non-metric units, and vice versa.

<span class="mw-page-title-main">Rimfire ammunition</span> Type of ammunition that is only commonly found in small-caliber firearms

A rimfire cartridge is a type of firearm metallic cartridge whose 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 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 early to mid-19th century onwards, such as pinfire, only small caliber rimfire and centerfire cartridges have survived to the present day with regular usage. The .22 Long Rifle rimfire cartridge, introduced in 1887, is by far the most common ammunition in the world today in terms of units manufactured and sold.

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

The .22 Long Rifle, also known as the .22 LR or 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 firearms including rifles, pistols, revolvers, and submachine guns.

<span class="mw-page-title-main">.30 Carbine</span> Light rifle cartridge for M1 Carbine

The .30 Carbine (7.62×33mm) is a rimless carbine/rifle cartridge used in the M1 carbine introduced in the 1940s. It is a light rifle round designed to be fired from the M1 carbine's 18-inch (458 mm) barrel.

<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">6.5×55mm Swedish</span> Nordic 6mm centerfire cartridge

6.5×55mm Swedish, also known simply as 6.5×55mm, 6.5x55 SE, 6.5x55 Swede, or in its native military as 6.5 mm patron m/94, meaning "6.5 mm cartridge model 94", referring to 1894, is a first-generation smokeless powder rimless bottlenecked rifle cartridge. The cartridge has most users in the Scandinavian countries, where it is known as the 6,5×55 or just "the 6,5".

<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 Magnum 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">.17 HM2</span> Rimfire cartridge

The .17 Hornady Mach 2, or .17 HM2, is a rimfire cartridge introduced in 2004 by the ammunition manufacturer Hornady, following the successful launch in 2002 of the .17 HMR. The .17 HM2 is based on the .22 Long Rifle "Stinger" case, necked down to .17 caliber and using a bullet weighing less than half the weight of a typical .22 Long Rifle bullet.

<span class="mw-page-title-main">6.5mm Grendel</span> Rifle cartridge

The 6.5mm Grendel is an intermediate cartridge jointly designed by British-American armorer Bill Alexander, competitive shooter Arne Brennan and Lapua ballistician Janne Pohjoispää, as a low-recoil, high-precision rifle cartridge specifically for the AR-15 platform at medium/long range. It is an improved variation of the 6.5mm PPC.

The 5.8×42mm / DBP87 is a military bottlenecked intermediate cartridge developed in the People's Republic of China. There is limited information on this cartridge, although the People's Liberation Army claims that it is superior to the 5.56×45mm NATO and Soviet 5.45×39mm 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.

<span class="mw-page-title-main">.44 Henry</span> Rimfire revolver and rifle cartridge

The .44 Henry, also known as the .44 Henry Flat, the .44 Rimfire, the .44 Long Rimfire, and the 11x23mmR in Europe, is a rimfire rifle and handgun cartridge featuring a .875 in (22.2 mm)-long brass or copper case. The round has a total overall length of 1.345 in (34.2 mm), with a 200 or 216 gr .446 in (11.3 mm)-diameter cast solid-lead heeled bullet. The original propellant load is 26 to 28 gr of black powder. The round has a muzzle velocity of approximately 1,125 ft/s (343 m/s), giving a muzzle energy of 568 foot-pounds.

<span class="mw-page-title-main">.300 AAC Blackout</span> Rifle cartridge originally designed for use in the M4 carbine

The .300 AAC Blackout, also known as 7.62×35mm, is an intermediate cartridge developed in the United States by Advanced Armament Corporation (AAC) for use in the M4 carbine. The cartridge yields increased performance in shorter barrels and effective subsonic performance for silencer use when compared to 5.56mm NATO. The .300 AAC Blackout uses standard 5.56mm NATO magazines and components with the exception of the barrel.

<span class="mw-page-title-main">HK 4.6×30mm</span> PDW cartridge designed for HK MP7

The 4.6×30mm cartridge is a small-caliber, high-velocity, smokeless powder, rebated, bottleneck, centerfire cartridge designed for personal defense weapons (PDW) developed by German armament manufacturer Heckler & Koch (HK) in 1999. It was designed primarily for the MP7 PDW to minimize weight and recoil, while increasing penetration of body armor. It features a pointed, steel-core, brass-jacketed bullet.

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, 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).

The .277 Fury or 6.8×51mm Common Cartridge, is a centerfire rimless bottlenecked rifle cartridge announced by SIG Sauer in late 2019. Its hybrid three-piece cartridge case has a steel case head and brass body connected by an aluminum locking washer to support the high chamber pressure of 80,000 psi (551.6 MPa).

References

  1. 1 2 3 "4,5x26R : Guns / Metric".
  2. 1 2 "Interdynamics MKR". Modern Firearms. October 27, 2010.
  3. "Wymiary łusek - Forum Broni Strzeleckiej". strzelecka.net.