Intermediate cartridge

Service rifle cartridge cases: (Left to right) full power cartridges 7.62×54mmR, 7.62×51mm NATO, intermediate cartridges: 7.62×39mm, 5.56×45mm NATO, 5.45×39mm.

Sturmgewehr 44 (Germany). Its development began in earnest with the Maschinenkarabiner project

An intermediate cartridge is a rifle/carbine cartridge that is less powerful than typical full-power battle rifle cartridges, such as the .303 British, 7.62×54mmR, 7.92×57mm Mauser or .30-06 Springfield, but still has significantly longer effective range than pistol cartridges. As their recoil is significantly reduced compared to high power rifle cartridges, fully automatic rifles firing intermediate cartridges are relatively easy to control. However, even though less powerful than a traditional rifle cartridge, the ballistics are still sufficient for an effective range of 250–500 metres (270–550 yd), which are the maximum typical engagement ranges in modern combat, at longer ranges intermediate cartridge bullets lose too much speed due of their small mass, which turns into huge decrease in energy and impulse. This allowed for the development of the assault rifle, a selective fire weapon that is more compact and lighter than rifles that fire full power cartridges. The first intermediate cartridge to see widespread service was the German 7.92×33mm Kurz used in the StG 44. Other notable examples include the Soviet 7.62×39mm used in the AK-47 and AKM series, and the American 5.56×45mm NATO cartridge first used in the M16.

History

The Second World War saw the use of the bolt-action rifles such as the Mauser Karabiner 98k, the Lee–Enfield SMLE, the Mosin–Nagant, the Arisaka Type 38, and Type 99 rifles, and during the early years, the Springfield M1903, as well as semi-automatic battle rifles such as the Gewehr 43, the M1 Garand, and the SVT-40. These rifles weighed over 8 lb (3.6 kg), and they were longer than 40 in (1,000 mm) and as such inappropriate for close combat. They fired cartridges capable of killing out to 1,000 m (1,100 yd). In close quarter combat, all the major armies began employing submachine guns such as the PPSh-41, Thompson M1928A1, and the MP-40, all of which fired pistol cartridges. Compared with the battle rifles, these submachine guns could provide high rates of controllable fire, but they lacked the power and longer effective range of the battle rifles.

Bolt-action rifles in use at the time were long and heavy, and their rate of fire was only around 10 - 15 rounds per minute. The bolt-action rifles were effective up to 800–1,000 metres (870–1,090 yd) in the hands of a trained marksman, but typical combat ranges were much shorter, around 150–300 metres (160–330 yd), rarely exceeding 500 metres (550 yd). Therefore, the potential of the rifle ammunition at longer ranges was seldom needed.

"...if hasty wartime training was such that he [the infantryman] had no better than a fifty percent chance of hitting a target at 300 yards (270 m), there was no logical reason to give him a rifle and ammunition designed to kill at 2,000 yards (1,800 m)"

— Ian V. Hogg, Modern Small Arms

What was needed was a more compact, selective fire weapon firing a cartridge combining the power of a rifle and the controllability of pistol cartridges. The resulting cartridge would have the accuracy of the former for typical combat ranges, and the firepower of the latter at short ranges.

The first cartridge fulfilling this requirement may have been the Japanese 6.5×50mm Arisaka used by the Russian Fedorov Avtomat rifle since 1915 (the cartridge itself dates back to 1897). The Fedorov was arguably the first assault rifle. Later came the US .30 Carbine, developed as a weapon for officers and rear area soldiers unlikely to be involved in infantry assault, but needing a weapon more effective than a pistol. Soon after came the 7.92×33mm Kurz round developed by the Germans in 1938, which was a shortened version of the standard 7.92×57mm Mauser round, and was used in another candidate for first assault rifle, the StG-44. When the Soviets developed the AK-47, they already had an intermediate cartridge of their own, so they adopted the gas operation system of the StG-44, which was extremely reliable.

Since the 1960s NATO, the (former) Warsaw Pact, the People's Republic of China, and other countries adapted relatively small sized, light weight, high velocity military intermediate service cartridges in the form of the 5.56×45mm NATO, Soviet 5.45×39mm, and Chinese 5.8×42mm. These intermediate cartridges allow a soldier to carry more ammunition for the same weight compared to their larger and heavier predecessor cartridges, have favourable maximum point-blank range or "battle zero" characteristics and produce relatively low bolt thrust and free recoil impulse, favouring light weight arms design and automatic fire accuracy.

Characteristics

Typical intermediate cartridges have:

• Cartridge case capacities ranging between 1.75–2.79 ml (27.0–43.1 grains H₂O)
• According to the official C.I.P. (Commission Internationale Permanente pour l'Epreuve des Armes à Feu Portatives) and NATO EPVAT rulings the maximum service pressures range between 340.00–430.00 MPa (49,313–62,366 psi) P_max piezo pressure
• Bullet weights ranging between 3–9 g (46–139 gr)
• muzzle energies ranging between 1,328–2,717 J (979–2,004 ft⋅lbf)
• Muzzle velocities ranging between 685–940 m/s (2,247–3,084 ft/s)

List of intermediate cartridges

Service cartridges

Service cartridges are cartridges the service rifles of armies were or are chambered for.

• 5.45×39mm cartridge of the AK-74 assault rifle
• 5.56×45mm NATO cartridge of the M16 assault rifle
• 5.8×42mm cartridge of the QBZ-95 assault rifle
• 7.62×39mm cartridge of the AK-47 assault rifle
• 7.92×33mm cartridge of the Sturmgewehr 44 assault rifle

Prototype cartridges

• 4.85×49mm chambered in the Enfield IW assault rifle
• 6.5 Grendel
• .280 British cartridge of the experimental EM-2 assault rifle
• 6.5 Grendel
• 6.8mm Remington SPC
• 7.5×38mm chambered for the CEAM Modèle 1950 rifle and experimental French variant of StG 45(M) rifle
• 7.65×33mm Argentine variant of German 7.92×33mm cartridge for use in Argentine copy of German Sturmgewehr 44 assault rifle
• 7.65×35mm chambered in CEAM Modèle 1950 and experimental French variant of the StG 45(M) rifle
• 7.75×39mm GeCo the first intermediate round ever made, German experiment

See also

• List of assault rifles
• Table of handgun and rifle cartridges

External links

• Assault Rights and their Ammunition: History and Perspectives