Intermediate cartridge



An intermediate cartridge is a military assault rifle cartridge that is less powerful than typical full power battle rifle cartridges such as the United Kingdom .303 British, Russian 7.62×54mmR, German 7.92×57mm Mauser or United States .30-06 Springfield, but still significantly more powerful 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 –, which are the maximum typical engagement ranges in combat. This allowed for the development of the assault rifle concept, which is a selective fire weapon that is more compact and lighter than rifles firing full power cartridges. The first intermediate cartridge to see widespread service was the German 7.92x33mm Kurz. Other examples include the Soviet 7.62x39mm used in the AK-47 and AKM series, and the .280 British round developed for the EM-2. The 5.56x45mm NATO cartridge is also an intermediate cartridge.

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, and they were longer than 40 in and as such inappropriate for close combat. They fired cartridges capable of killing out to 1000 m. 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 considerably 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 – in the hands of a trained marksman, but typical combat ranges were much shorter, around 150 –, and most of the time they did not exceed 500 m. 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 yd, there was no logical reason to give him a rifle and ammunition designed to kill at 2000 yd""

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 6.5x50mm 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 7.92x33mm Kurz round developed by the Germans in 1938, which was a shortened version of the standard 7.92x57mm 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 making it an ideal field weapon.

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 and produce relatively low bolt thrust and free recoil impulse, favouring light weight arms design and automatic fire accuracy.

Performance
Typical characteristics of an intermediate cartridge are Kinetic energy ranges between 1350 - 2700 J, muzzle velocities of 600 - 900 m/s and bullets of 3 - 9 g.