The following information is from the Russian book “Secrets of Russian Artillery” by Aleksandr Schirokorad, published in 2003. These excerpts were translated from Russian and kindly sent to us by Alex Diehl; I slightly edited them for this page. Aleksandr Schirokorad also wrote a book on aircraft armament.

Note: remarks written in double brackets ((abc abc abc)) are the translator’s comments and were not part of the original text.

ARKON

In January 1934 KONDAKOV and TOLOCHKOV revealed their 76 mm recoilless aircraft gun, in competition to KURCHEVSKI’s and TUKHACHEVSKI’s 76 mm recoilless gun. KONDAKOV was ordered to build a 45 mm version of his gun first. This was done at the OKB “AU”. This 45 mm gun was built and tested successfully. KONDAKOV’s gun was gas operated, with a gas port in the barrel. The gun was fed by a 6 round clip. The cartridge cases were made of brass. During operation (firing) the gun barrel moved forward for 450 mm, ejected the fired case, and loaded the next. The cartridges were electrically primed.

In 1936 development of the 37 mm ARKON (Avtomaticheskaya Reaktivnaya Kondakova) was finished. The gun was gas operated and had a magazine which held 5 rounds. The cartridges had brass cases with plastic bases. The vertical breech had a built-in venturi nozzle which moved together with the breech.

Data:
Gun weight: 40 kg
Projectile weight: 0.674 kg
Charge weight: 0.175 kg
Vo: 545 m/s

The gun was installed on an R-6 aircraft and till the end of 1936 firing tests were carried out. For unknown reasons the work on this gun was cancelled.

RPTR

In 1937 KONDAKOV developed the RPTR 37 mm recoilless gun. The gun was gas operated. The cartridge cases were made of brass and had hemispherical shaped plastic bases. The gun had a 5 round magazine, on top of the gun, and a vertical breech with built-in venturi nozzle. The gun had a wheeled mount and was broken down for manual transport if needed. The experimental RPTR was tested already at the end of 1936 by NIAP. 

The cartridge for this gun was taken from the M 1930 anti tank gun ((must have been modified then unless the M 1930 was recoilless as well)). Factory No 7 got ordered to produce 30 units of the RPTR. Serial production never started, because the recoilless weapon programme was cancelled.

Data:
Caliber: 37 mmData:
Barrel length with venturi: 1550 mm
Length of whole weapon system: 1650 mm
Gun weight on wheeled mount: 63 kg
Rate of fire: 30 rounds/minute (practical)
Projectile weight: 0.674 kg
Fuze: MD-5
Charge weight: 0.175 kg
Vo: 545 m/s
Gas pressure: 2450 kg/cm2

GK-37 and GK-45

Parallel to the RPTR, KONDAKOV developed the aircraft guns GK-37 and GK-45 with inert counter projectiles. Both guns were identical, except for their calibers. The guns had two barrels which pointed in opposite directions and shared one chamber. One barrel fired the live projectile and the other the inert one. Both barrels could be used for live firing just by exchanging the position of the cartridge for the inert and the live projectile. The gun was gas operated and had gas ports in the barrels.

The GK-45 had an ammunition capacity of 5 live rounds and 5 rounds with inert projectiles. The GK-37 had a capacity of 3 plus 3 rounds. The wing-mounted version of the GK-37 had a capacity of 12 plus 12 rounds. The guns had electrical triggers. The GK-37 was planned for the “Bomber Fighter” aircraft “BI” which was developed by V.D. BOLCHOVITINOV. The gun was operated in flight by two crew members, one of them a gun loader. Ballistics of the GK-37 were identical to those of the AKT-37. The ballistics of the GK-45 were identical to those of the M 1932 anti-tank gun, which used the same ammunition.

In November 1936 NIAP started ground firing trials of the GK-45. During these tests a glass filled with water was put on top of the gun, and remained there without loss of water. On 18 December 1936 the GK-45 was tested at an 80 degree angle in a ground based mount but failed to fire in automatic mode: It was not reloading because the barrels did not separate properly. After an exchange of the main springs the gun mechanism worked as expected.

The final report on the firing trials was published on 23 April 1937 by NIAP. In the beginning of 1937 it was decided to produce an experimental series of the GK-37. The factory “Barrikady” (barricades) was ordered to deliver 35 barrels for the GK-37 by 1 April 1937. At this time the programme on recoilless weapons got discredited and by order from “above” all work was halted.

Data:	GK-45	GK-37
Barrel weight	2 x 94.2 kg	2 x 37.2 kg
Weight of one cartridge clip	31.3 kg	8.9 kg
Gun weight	340 kg	140 kg
Rate of fire	60 rounds per minute during trials	140 rounds per minute (theoretical)
Projectile weight	1.425 kg	0.6 kg
Vo	758 m/s	940 m/s

DRP-76

In 1942, when Russia observed recoilless weapons in use with the German army, the interest in this kind of weapon was revived. By order of Stalin a special commission was established which started to review all data from the 1930s projects. In relation to this Stalin made a remark about the affair around Kurchevski ((seems that he was disliked before)). From this moment on, several development bureaus started to work on recoilless weapons. Some of them were TsAKB of Grabin and OKB-172.

Between 1943 and 1948 OKB-43 developed several recoilless aircraft guns. Based on one of them, in 1953 a naval 76 mm recoilless gun for torpedo boats was developed, designated DRP-76. The gun was belt fed and remote controlled. This gun was not adopted for service.

Data:
Caliber: 76 mm
Barrel length in calibers: 30 cal
Gun weight: 150 kg
Crew: 2 men
Projectile weight: 4.6 kg
Cartridge weight: 8.75 kg
Vo: 530 m/s
Firing distance: 11 300 m

AKT-37

In 1932 KONDAKOV and TOLOCHKOV started to develop an universal 37 mm gun designated as AKT-37 (earlier as AKT-2). AKT stands for “Avtomat Kondakova-Tolochkova”. The guns purpose was to be used in an anti-aircraft mount as well as in aircraft.

Aircraft cannot cope very well with high recoil forces, therefore these guns were designed to maximize the weight of the backward moving parts of a gun during the recoil process, to reduce recoil. For this reason the whole barrel was included into the recoil process and also the magazine was part of the moving weight. The gun had an unique accelerator for the breech which worked in both directions.

At the beginning of the project the barrel as well as the ammunition of the 37 mm Rheinmetall automatic gun (4K) were used ((Flak 18?)). The system was based on a short barrel recoil with a monoblock barrel which was quick-exchangeable. The gun had a hydraulic recoil brake and a spring for forward movement. The gun had a magazine capacity of 5 rounds. After the last round was fired the breech remained in the rear position to ease the reloading and safe the crew from the reloading procedure. The rate of fire was 200 rounds/minute and the recoil force was 700 kg.

Problems with this gun were failures of the mechanism and problems in regulating the recoil. Reloading was difficult because the magazine was one of the moving parts.

An experimental pattern was built in the Artillery Academy in the beginning of 1935. After a long break the gun was undergoing trials at NIAP, beginning on 4 May 1936. The firing trials were conducted between 16 May and 11 June 1936. For the firing trials a temporary mount was used.

After the firing trials on the ground were finished, the gun was installed in the R-6 aircraft. The firing trials in air lasted from 8 August till 16 August 1936 and were carried out at Noginsk shooting range. From the gun mounted in the R-6 201 rounds were fired. During this the gun had 5 malfunctions of the mechanism which occurred in steep flying angles of the aircraft, which prevented the breech from moving fully into the forward position. 

The AKT-37 passed the air force tests and 10 guns were ordered for aircraft installation in the bombers SB and DB-3. For anti-aircraft use the AKT-37 was projected to be used in the LAKT and TAKT mounts. The LAKT was a light two-wheeled mount. To deploy for firing, the whole weapon system was lowered and the wheels were pulled away with their frame. The TAKT was a mount was for use on the loading platform of a truck, or for use on a four wheel mount designated ZU-7 and made by the Bryansk factory. The appearance was similar to the Bofors mount system.

Between 1936 and 1938 the factory No 7 manufactured 15 AKT-37 and Factory No 4 (Voroshilov) manufactured 4. On 3 October 1937 NIAP received an AKT-37 on a TAKT mount on a ZIS-12 truck. The barrel elevation was +80 degrees. Between 23 and 28 April 1938 NIAP tested the AKT-37 on the ZU-7 mount. During the trials 52 rounds were fired and the 340 km were passed behind a GAZ-AA truck. Between 5 October and 10 December 1938 NIAP conducted an anti-aircraft gun competition in which the AKT-37 was participating on the mounts LAKT-37 and TAKT-37 (ZU-7). On 25 December 1938 the commission stated that the AKT-37 on both mounts had a too short firing distance and that improvements would not make any sense. With this, all work on the AKT-37 was cancelled.

At a projectile weight of 0.63 kg and a propelling charge weight of 0.2 kg (powder 9/1 NGV), the Vo was 940 m/s and the chamber pressure was 2850 kg/cm2. At a projectile weight of 0.645 kg and a propelling charge weight of 0.19 kg (powder 85/185 NGV), the Vo was 850 m/s and the chamber pressure was 2400 kg/cm2. In the beginning the case length was 265 mm and in the end of 1936 it was shortened to 240 mm.

Data:
Caliber: 37 mm
Length of gun only: 3050 mm
Barrel length: 1900 mm (51.3 calibers)
Length of rifled part of barrel: 1652 mm
Barrel twist: 50 calibers
Angle of rifling: 3°35’43”
Barrel twist at muzzle: 30 calibers
Angle of rifling at muzzle: 5°58’42”
Depth of rifling: 0.45 mm
Width of rifling: 4.8 mm
Width of fields: 2.5 mm
Weight of magazine holding 5 rounds: 12.5 kg
Maximum recoil: 160 mm
Minimum recoil (for operating gun): 153-155 mm
Rate of fire: 150-200 rounds/minute (on different firing trials)

ASKON-37

Already in 1936 KONDAKOV did not wait for the results of governmental firing trials and started to rework and modify the AKT-37. The result was the “rapid fire” ASKON-37 gun. The rate of fire was 250 rounds/minute and the Vo was 1060 m/s. The major differences between the AKT and the ASKON were:

• The barrel was fluted and reinforced, to increase its strength and improve cooling.
• The feeding mechanism was improved and got an accelerator. 
• The magazine was made not to recoil. The recoil was shortened to 117 mm, which raised the rate of fire.

Like the AKT the ASKON was designed for anti-aircraft and aircraft use. The first experimental ASKON-37 was handed over for trials on 13 May 1938. At the end of 1938 the gun was installed on a ZU-7 mount. The ASKON was still a complicated gun and KONDAKOV had many enemies, so the work on all KONDAKOV guns was cancelled again.

Data:
Caliber: 37 mm
Length of gun: 3318 mm
Length of barrel: 2335 mm (63.1 calibers)
Barrel twist: 30 calibers
Riflings: 16
Depth of rifling: 0.45 mm
Width of fields: 2.5 mm
Cartridge: drawing 6436 (ANIMIN)
Weight of projectile: 0.645 kg
Weight of propellant charge: 0.378 kg
Vo: 1060 m/s
Firing distance: 2900 m

AKON-45

In 1935-1936 KONDAKOV developed an automatic aircraft gun of 45 mm caliber. This gun was gas operated. The barrel was a quick-exchangeable, air-cooled monoblock barrel. The gun had a 5 round magazine. In the beginning of 1937 OKB-43 built an experimental version of this gun which was designated AKON-45. Data on the mount is not available. Trials with this gun have been carried out on an old 76 mm M 1914/15 gun mount.

In May 1938 all works on this gun were cancelled because KONDAKOV agreed on cancelling this project after exchanging letters with the artillery directorate. KONDAKOV’s real reasons for giving up are not known.

Data:
Caliber: 45 mm
Barrel length: 2370 mm (52.7 calibers)
Length of rifled part: 2048 mm
Barrel twist: 30 calibers
Riflings: 16
Depth of rifling: 0.5 mm
Width of rifling: 6.5 mm
Rate of fire: 100-120 rounds/minute
Projectile weight: 1.425 kg
Weight or propelling charge: 0.405 kg (powder 7/7)
Vo: 800 m/s
Firing distance: 2690 m