Rikhter R-23

The Rikhter R-23 is an aircraft autocannon developed for the Soviet Air Force.

In the late 1940s and the early 1950s tests with defensive bomber turret cannons resulted in problems caused by the air flow affecting the weapons' barrel. Therefore a turret cannon had to be developed in the 1950s, whose short barrel provided a minimum area for the air flow to act on. A competition between OKB-16 and the design bureau in Tula was held, which led to the adoption of the R-23 and the AM-23 cannon. Aron Abramovich Rikhter from OKB-16 had the idea to create a highly compact weapon by using the revolver principle and by installing the feed mechanism in front of the revolver cylinder. This way the overall length of the cannon was just as long as the length of the barrel plus the length of the cylinder. The feed mechanism was close to the cannon's centre of gravity, which was especially favourable when traversing and elevating the weapon. However, a feed mechanism that chambered the rounds base-first from the front of the weapon required a cartridge completely different from the usual design. A telescoped cartridge that completely contained the projectile inside the cartridge case was therefore developed by GSKB-398 (today GNPP “PRIBOR”).

Despite some initial problems with the gun the engineers at OKB-16 persevered with the design and the first 261-P prototype cannon was produced in 1957. On August 7th 1964 the cannon was adopted and received the official designation R-23. The 23mm Rikhter cannon is installed in the DK-20 tail turret of the “A”, “B”, “K” and “R” versions of the Tu-22 bomber only. The hydraulically elevated and traversed DK-20 turret uses the radar sight “Krypton” and the television sights TP-1 or TP-1A. Fired cartridge cases are ejected outside the aircraft. The DK-20 turret weighs 593kg including the R-23 cannon and 500 rounds of ammunition.

Next and much more unique application found the cannon in the Soviet space program. It was mounted on the military space station ALMAZ/Salyut 3/OPS-2 as selfdefence weapon and at the end of the mission, when the station flew unmanned mode, was tested and successfully fired. This "space cannon" had supply of 32 rounds.

Mechanism
The 23mm R-23 is a gas-operated revolver cannon whose revolver cylinder has 4 cartridge chambers. Three separate gas systems eject the fired cartridge case from the chamber, chamber a fresh round and drive the revolver cylinder and the feed mechanism. To reduce the overall length of the weapon, the feed mechanism is located in front of the revolver cylinder and chambers the cartridges backwards. The ammunition is fed from the right side only and consists of a belt that contains the cartridges in disintegrating belt links. The latter drop out on the left side of the receiver. Fired cases are ejected forwards on the right side of the receiver. With up to 2,600 rpm the R-23 was the fastest firing single-barrel cannon ever introduced into service.

The R-23 cannon has an automatic charging mechanism that fires the cannon in case of a misfire. When one of the two pyrotechnical cartridges is fired, a small bolt inside that cartridge is accelerated to penetrate the side wall of the R-23 cartridge. The hot propellant gases of the pyrotechnical cartridge follow the bolt into the dud R-23 cartridge and ignite the propellant charge to fire the round. This unique and curious mechanism was obviously used in the R-23 cannon for the first time. The same kind of mechanism with a single pyrotechnical cartridge was later incorporated into the 30mm GSh-301 aircraft cannon.

Secrecy
The 23mm Rikhter aircraft cannon and its unique telescoped ammunition remained a military secret for a long time. This can be partially explained by the fact that the R-23 cannon was used in outer space, arming Soviet space stations. Developed in the second half of the 1950s, the R-23 cannon was known only in the Soviet Union until the Tu-22 bomber was exported to Iraq and Libya during the 1970s. Those countries in the Middle East were the first outside the Soviet Union to learn about the defensive revolver cannon and its curious ammunition. The 23mm Rikhter cannon and its ammunition was brought to the attention of French EOD personnel when a Libyan Tu-22B was shot down by a French MIM-23B Hawk SAM battery in Chad in 1987. The Israeli army had discovered the 23mm Rikhter ammunition even before the French, without knowing what kind of weapon it was used with. During the Israeli occupation of South Lebanon from June 1982 to June 1985, the Israeli army captured a crate of R-23 ammunition. This crate was delivered by mistake within a shipment of Soviet 23mm ZSU cartridges. This anti-aircraft ammunition was originally shipped to Syria and ended up in Lebanon, where it was found by the Israeli army.

Ammunition specifications

 * Cartridge dimensions: caliber 23x260 (telescoped) with a steel case
 * Projectile weight: 175 grams
 * Propellant charge: 67 g of 4/7fl VBP smokeless powder
 * Types of ammunition: HEI (nose fuzed), HEI (base fuzed), [Target practice|TP] airburst, TP (inert)