CZK - R 11 (100 mm protilietadlový kanón)

Negotiations on the requirement for the development of a new 100 mm anti-aircraft gun took place at the Škoda Plzeň company in 1948 and 1949. The company received the development of this cannon on the basis of DKS No. 4 of 31 July 1948. The development programme received the designation R 11. Škoda produced drawings (drawings Zb 5425 P, Zb 5426 P and Zb 5427 P dated 8 November 1948).
On 24.1.1949, VTU commissioned the production of the prototype. The specifications were changed several times. The weapon was to be designed for indirect fire using a central sight with the possibility of direct fire against air and ground targets.
The design of the weapon consisted of a monobloc barrel, a replaceable cartridge case, a detachable rear part of the barrel and a muzzle brake. The breech was designed as a horizontal wedge with electric firing. The gun was to have automatic loading, which was based on the tested 5-round feeder on the 8.8 cm PLK vz. 41 N. The MNO required a high cadence of up to 25 rounds per minute in a firing duration of at least 7.5 minutes. The barrel had to withstand at least 1,500 shots, later the requirement was increased to 2,000-2,500 shots. The signal receivers from the central sight and the electric drives were to be of similar design to the German vz. 37 N. Due to the complexity of the design of this fire control system, it was temporarily abandoned, later it was planned to retrofit it from the German railway 105 mm PLK vz. 39 N. The ammunition chamber and some of the ammunition had a common development with the AK 1 tank gun and the A 20 anti-tank gun. For direct fire against aircraft and ground targets, the gun was to have a detachable sight of the vz. 47 with a 3x8° telescope. The prototype gun was to have a protective shield for the operator. The gun was to be transported on a pair of detachable German Type 2 chassis.
At a meeting in Škoda Plzeň on 2 March 1949 to 4 March 1949, it was decided that the program would not be started until 1950, until then only preparations for the project were to take place. The plan envisaged building a prototype only in early 1953, serial production was not to start until the second five-year period.
On 28.9.1949 and 29.9.1949 it was decided to build a wooden model. To accelerate the program, the VTU counted on mounting a pair of experimental barrels on the bayonets of German 15 cm howitzers vz. 18 N.
Open was the unification with the Soviet 100 mm gun vz. 44 S. The Soviet side did not respond to the request to supply the documents, but after an agreement with Soviet advisors in early 10/1950, the project using Czechoslovak ammunition was approved and a waiver was granted.
The challenging development was prolonged, with the estimate of the first gun deliveries not being made until 7/1955. The first prototype was to be delivered on a cross-launcher, but from 1951 onwards the State Territorial Air Defence Command required a folding chassis, which the subsequent prototypes were to have. The first guns delivered were to receive central sights from 85 mm PLK vz. 44 S. A newly developed electric central sight (ECS) was intended for further production, but its development was not successful.
Development was continually prolonged, the delay being influenced by a number of circumstances. From an extraordinary event, when a worker of ZKJV Dubnica nad Váhom was killed during test firing on 26.6.1952, to the transfer of the design office from Plzeň to the national enterprise Konštrukta Trenčín. Probably at least three prototypes of serial numbers 274, 3635 and 3636 were produced in 1953 and 1954. Control tests were carried out in 1955. Successful firings in the Baltic region of Poland followed, with the last documented firings taking place in Trencin in late 11/1956. During the firing tests 61 rounds were fired with mostly positive results. The reloading equipment was not reliable. The gun with PUAZO sight and EUZ 4 passed the tests. Tests in the Soviet Union were planned, but these were probably abandoned. According to a memo dated 12.4.1957, the prototype gun with a stock of 600 rounds was to be used in the development of the EUZ I and EUZ II central sights and the dispersion of the S 45 artillery fuzes was to be ascertained.
The cannon still underwent comparison in 1957 with the Soviet 100 mm anti-aircraft KS-19, whose Czechoslovak licensed production had been approved in 1955.
The R-11 gun was world-leading in terms of parameters, but it came too late. The age of rockets had arrived and large-calibre cannons were by then already outdated.
The prototype is preserved in the technical museum in Lesany.

Mgr. Martin Dubánek - Od bodáku po tryskáče - Nedokončené Československé zbrojní projekty 1945-1955, Mladá fronta 2011, ISBN : 978-80-204-2515-7