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The NR-30 Aircraft Mounted Weapon


The NR-30 aircraft cannon was designed by Soviet designers A. E. Nudelman and A. A. Richter in the mid-1950s. The name of the weapon was derived from the initials of their surnames (Nudelman, Richter) and the number ‘30’ refers to the weapon’s caliber. This period was characterized by a great boom in the design and production of new types of jet aircraft in the Soviet Union and, by extension, their internal gun armament. This specific cannon was gradually installed in the Mikoyan-Gurevich MiG-19S fighter (three in the nose of the aircraft, all equipped with a muzzle brake at the end of the barrel), the supersonic MiG-21F (on the right side of the fuselage, below the cockpit), the Sukhoi Su-7BM, BKL fighter-bombers (one in each wing root, just behind the cockpit, without muzzle brakes) and later the Su-17 M3, M4, UM-3 (the latter two-seat version with only one cannon in the right wing) and its export variants Su-22M3, M4, UM-3K, with a like number of cannons as the Su-7. Due to the political division of the world at that time and the existence of a military grouping of countries in the socialist camp, called the Warsaw Pact, the above-mentioned types gradually entered the inventory of the air force of the former ČSLA (Czechoslovak People's Army). The ammunition was initially produced in and imported from the Soviet Union, but later it began to be produced in Czechoslovakia, initially under license, but later as an evolution under its own development program. The weapon was designed to deal with aerial as well as ground targets effectively.

 TEXT: Tomáš Dedera


The NR-30 cannon is an automatic weapon with a continuous, double-sided belt feed, the operation of which is based on the principle of using recoil energy with a short barrel recoil. During barrel recoil, the rotary bolt is unlocked and accelerated backward by a lever accelerator. A gas gate is used to brake the barrel recoil and bring it back to its forward position - it uses gunpowder gases taken from within the gun barrel. These gases are fed into the gas cylinder through channels and fill the working space in front, sealed by the piston and at the rear by inserts with sealing rings. During barrel recoil, the barrel collar first hits the piston, causing it to move with the collar and the barrel as the recoil continues. The gas channels are closed off by engaging the insert sealing rings and the gases in the gas cylinder are compressed. Their pressure exerts a force on the piston surface that slows the barrel's backward momentum and, after stopping, returns it to the forward position. Just before reaching this forward position, the gunpowder gases from the cylinder are blown out of the system.

 

The simple rifled barrel is supplemented with a muzzle brake in some variants of the weapon, which simultaneously functions as a flame suppressor and directs the escaping exhaust gases outside the aircraft. The gun is cocked pneumatically (by compressed air), and fired electronically, by releasing the bolt from the rear position. The electric trigger circuit includes a round counter and a signal indicating the need for pneumatic cocking. A silencer is inserted between the weapon and its mount in the aircraft.

 

NR-30 Technical Specifications

 

Caliber 30 x 155B mm Number of rifled Grooves in the Barrel 16 Initial Muzzle Velocity 780±10 m/s Weight 66,5 kg Firing Rate minimum 850 rounds per minute Ammunition Round Weight 410 g Minimum Air Pressure for Automatic Cocking 3.8 MPa Recoil Force max. 6000 kg Recoil Length - Barrel 100 mm Recoil Length - Bolt 302 mm

 

Main NR-30 Components and their Function

 

Barrel – Defines round direction, speed and rotation, thanks to a rifled bore with sixteen rotations, in the form of a right-handed thread. In the middle of the barrel length there are 10 holes for the discharge of exhaust gases into the gas cylinder. In the rear part of the barrel there is a bullet-shaped cartridge chamber.

 

Breech Casing – This item is connected to the barrel and moves 100 mm back and forth with it in the gun housing when firing.

 

Breech – Consists of the head and body of the breech assembly. The feeder inserts the cartridge into the head of the breech, the bolt inserts the cartridge into the chamber and locks it. The cartridge is fired mechanically after the chamber is locked.

 

Gun Casing – Serves to guide the barrel and the breech block during firing, and also serves as locator for the weapon control mechanisms – the feeder, trigger, cocking cylinder and accelerators. The gun is attached to the aircraft structure via the gun casing. It is blocked off at the rear by a shutter.

 

Cocking Cylinder – Serves to cock the weapon by supplying compressed air at a pressure of 50atm, which moves a slide from the rear position and inserts a cartridge from the cartridge belt into the slide head. It also contains a preloaded spring, which is compressed during cocking. The slide is held in the rear position by a trigger.

 

Electromagnetic Trigger – Used to remotely control the firing of the cannon. After applying current, the bolt is released and thrown forward under the pressure of the preloaded spring.

 

Ammunition Feeder – Used to advance the cartridge link belt and insert the cartridges into the breech.

 

Gas Cylinder – Serves to dampen recoil when fired. Some of the exhaust gases are directed into it through holes in the barrel and are further compressed there. The floating piston is compressed by the barrel nut.

 

Recoil Accelerator – Serves to unlock the chamber after discharging a round. The accelerator lever transfers the movement of the barrel to the accelerator plate, which accelerates the movement of the bolt relative to the barrel, thereby rotating the bolt head and thus unlocking the chamber.

 

Pre-slide Accelerator – Serves to accelerate the movement of the breech with the cartridge into the chamber, thereby increasing the rate of fire.

 

Barrel Lock – Closes the rear part of the barrel housing, dampens the movement of the bolt at its rear position and keeps the cocking cylinder in the correct position. It is connected to the barrel housing by a thread.

barrel

 breech casting

breech

Overall view of the NR-30 aircraft cannon equipped with a muzzle break as would be found on, for example, the MiG-19S.


Principle behind Cannon Operation during Pneumatic Tensioning

 

By channeling compressed air from the pressure cylinder to the cocking cylinder of the weapon, the barrel with the breech block and the locked breech is pulled backwards. In the initial phase of the movement, the recoil accelerator is activated, which unlocks the chamber and moves the breech block to the rear position, where it is caught by a trigger. The barrel with the breech block is pulled further backwards to the rearmost position (100 mm). After releasing the cocking button, the compressed air returns the barrel with the breech block to the front position. The movement of the barrel backwards and forwards is simultaneously transmitted by gears to the ammunition feeder, which advances the cartridge belt by one round and inserts the cartridge into the breech block. This makes the weapon ready for firing. This is indicated in the cockpit by the lighting of a red indicator light after the electrical installation contacts in the trigger are engaged.

 

Principle behind Cannon Function during Firing

 

After applying electric current to the trigger of the weapon, the bolt is released, which, under the pressure of the tensioned spring inserts the round into the cartridge chamber and locks it. After locking, the round is mechanically fired. The resulting exhaust gases exert pressure on the bottom of the round and the bottom of the cartridge case. The round begins to move forward and the barrel with the breech block  backward. The effect of the recoil accelerator kicks in, the cartridge chamber is unlocked and the breech with the empty cartridge is moved backward, where it is captured by the electromagnetic trigger. At the moment when the round passes the vent holes in the barrel, some of the exhaust gases are released into the gas cylinder. As a result of the movement of the barrel, the gas cylinder space is closed and the resulting gases are compressed by a floating piston, which is moved by the barrel nut. Compressing the gases dampens the effects of recoil arising during the firing sequence. When the barrel reaches its rear position, it returns to the front position under the pressure of the gases in the gas cylinder. In the front position, the gases from the gas cylinder escape to the outside. The movement of the barrel is simultaneously transferred to the feeder, which moves the cartridge belt by one round and inserts another cartridge into the breech head. This pushes out the spent cartridge and ejects it outside the aircraft, while the ammunition belt links are channeled to a box for collecting them inside the aircraft. After returning the barrel to the front position, if the breech is in the rear position and electric current is still supplied to the trigger, the automatic operation of the firing sequence is repeated and the cannon fires another round.

 

NR-30 30x155B Ammunition Types

 

The development and the evolution of the NR-30 system was not limited to the weapon itself. The ammunition evolved as well. As noted earlier, the 30 designator refers to the caliber of ammunition used in millimeters, while 155 specifies the length of the cartridge, also in millimeters. During the development of the weapon, a range of ammunition types was also introduced:

OFZ (NATO Equivalent HEI) – high-explosive – incendiary with a head fuse, 

BR (APHE) – armor-piercing – high-explosive with a bottom fuse, PRL – anti-radar chaff,

LP (TP) – inert, for verifying the function of the weapon, 

FZ – high-explosive – incendiary (anti-balloon).

Later, the following types of rounds were developed and modified:

OFZ – modernized, ME – multi-element.

This does not complete the list of available rounds used in the NR-30. Those listed above are base types, used by the Czechoslovak and later, the Czech Republic Air Forces.


Two pieces of steel cartridge links designed for the NR-30 cannon, the articulated connections of the links allows the belt’s shaping within the ammunition box and in the supply sleeve to the cannon.

Belts inside the ammunition boxes of a Su-22M4 aircraft, the boxes, like the cannons in the wings, are offset relative to each other for spatial reasons.


Visual inspection confirming correct installation of the ammunition belt, the armament specialist holding the lid of the feed to the left NR-30 cannon of a Su-22M4. Photographed from the fuselage of the aircraft, from a modeling perspective, the vents in the wing and the overall operational wear around the blast cover are of note.


Detail of the right side of the fuselage of a MiG-21F below the cockpit, with elements of the mounting lugs for the installation of the NR – 30 cannon, which forms the basic gun armament of this type of aircraft.


NR–30 cannon in the right wing root of a Polish Air Force Su–22UM–3K aircraft. It is worth noting that the fuselage and wing parts were shielded with stainless steel metal panels (picture on the left before firing), in order to protect the surface from the undesirable effects of exhaust gases generated during firing (right).

Top view of the NR-30 cannon muzzle brake with exhaust gas vents.

The cannon in the previous photos, used as a instructional aid, was originally installed in the wing of a MiG-19S fighter (which can be derived from the shape of the exhaust vents on the muzzle brake).

Detail of the NR-30 cannon in the right, lower part of the nose of the aircraft. There is a clear difference in the number and shape of the exhaust vents and, as with other aircraft armed with the cannon in the wing root, the ever-present stainless steel blast shield embedded in the fuselage side. 

Detail of the right wing cannon – in the other pictures, there is a clear difference in the shape and number of exhaust vents of the muzzle brake, and as in the case of the Su-22, the adjacent fuselage of the aircraft is protected by a heat resistant steel panel, necessary for when the cannon is actually employed. 

Detail of the muzzle brake of the right wing cannon – the front part of the brake is worth noting, which is welded together from several parts, but they are not further mechanically modified and, overall, they look quite rough.

01/2025
Info EDUARD 01/2025

INFO Eduard is a monthly scale model-historical magazine published in Czech and English by Eduard Model Accessories since 2010. The magazine is available for free on the Triobo platform and can be downloaded in PDF format. Eduard is a manufacturer of plastic models and accessories with over 30 years of tradition. Throughout its history in the plastic modeling industry, Eduard has become one of the world's leaders. Further details about the company and its product range can be found at www.eduard.com. You can subscribe to the INFO magazine and receive product information for free at: https://www.eduard.com/cs/info-eduard/

 

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