Prior to the introduction of the NR-30, most Soviet autocannon were of 23 or 37 mm calibre and often used in combination. For instance, the Mikoyan-Gurevich MiG-15 was equipped with two NR-23's and a single N-37. The two were mismatched; the NR-23 was a rapid-fire weapon with relatively low explosive power, while the N-37 was extremely powerful, typically able to destroy a bomber with a single hit, but with very a low firing rate which made it unsuited to firing at manoeuvring targets like fighters. Moreover, the two had very different ballistics which meant that long-range fire would result in one or the other set of guns being properly aimed.
The NR-30 was an attempt to solve this problem by introducing a single weapon that could serve in both roles. It was essentially an enlarged version of the NR-23 using the same short recoil mechanism firing a new 400 gram 30 mm round that was roughly twice the mass of the earlier NR-23 and slightly less than half that of the N-37. While not capable of destroying a bomber in a single hit, it made up for this by improving the firing rate to 900 cycles per minute, beyond that of the NR-23. Muzzle velocity increased to 800 m/s, besting both the NR-23 and N-37.
Its total firepower, the product of per-round energy and firing rate, was better than either of the earlier weapons. This demanded the use of a muzzle brake with an integrated flame damper to prevent airframe damage from its firing. In fighters, wing mountings were more common than the nose mounts of the earlier designs. This often required small sections of stainless steel to be fitted to the wing skinning to protect it.
Aircraft typically carried a load of 70 shells for each gun. There were 20 different types of ammunition available; the most used were AP and HEI, the latter of 40–48 g HE internal charge, several times larger than 20 mm ammunition. An unusual munition was the Chaff dispenser PRL, with 48,000 chaff particles internally; it is not known how it was used.
The NR-30 was also remarkably light, about one-third lighter than the N-37 while offering higher firepower. The GSh-301 is the only lighter 30 mm gun.
The NR-30 was used mainly in the MiG-19, early MiG-21 models, the Sukhoi Su-7, and the Sukhoi Su-17. It was also used on the Shenyang J-6, the Chinese copy of the MiG-19, with a third gun in the nose. The Chinese manufactured their own version, the Type-30, basically similar though with slightly different characteristics.
