- Years of issue – 1939 – 1940
- Total released – no data
- Caliber – 20 mm
- Weight in firing position – 1464 kg
- Barrel length – 1300 mm
- The length of the threaded part – 1159.4 mm
- Calculation – 4 people
- Rate of fire – 420 – 480 rds / min
- The greatest firing range – 4800 m
- Direct shot range – no data
- Shooting angles:
- Horizontal – 360 °
- Vertical – 0 ° to + 85 °
The appearance in service in the late 1930s of the XX century of new, faster fighter planes and bombers in the armies of potential adversaries forced the leadership of the armed forces of the Third Reich to formulate a new task for the military industry. Anti-aircraft automatic cannons with a high rate of fire were required to defend against an air enemy.
In order to increase the density of anti-aircraft fire in October 1938, the design bureau of the Rheinmetall-Borsig concern began developing a fundamentally new 20-mm anti-aircraft multiple launch rocket systems, designated “SMK-18”. The tactical and technical assignment for their development provided that they should have a total weight of no more than 3600 kg; weight in firing position – no more than 1800 kg; the height of the line of fire – 1452 mm; firing angles: horizontally – 360 °, vertically from 0 ° to + 85 °; and the combat characteristics of the swinging units must correspond to the characteristics of the 20 mm Flak 18 anti-aircraft gun.
By February 1940, four variants of eight-barreled anti-aircraft multiple launch rocket systems, known as the “SMK-18 V1”, were created – two of them with a horizontal single-row arrangement of barrels and two with a double-row parallel (four in a row) arrangement of barrels. The first three variants were the swinging parts of the 20mm Flak 38 automatic naval anti-aircraft gun, and the swinging part of the fourth version was a new design of the 20mm anti-aircraft gun, all of which were mounted on carriages.
All samples of SMK-18 V1 anti-aircraft guns had 8 barrels, connected in one common body – a block, and their bolts were combined in one common bolt carrier. The action of the automatic mechanism of all systems was based on the recoil energy with a long stroke of the barrel with a long recoil of all the gates at the same time. If the new design of the fourth variant of the eight-barreled SMK-18 V1 cannon was a self-loading cannon, then the other three variants of the SMK-18 V1 were fully automatic. Their air-cooled barrels had an ordinary design, which was no different from the 2-cm Flak 38 cannon, and the barrel of the fourth version had a perforated cylindrical casing with air cooling, structurally similar to the barrel casing of the single MG.34 machine guns.
In machines with a horizontal arrangement of barrels, the gates had the same arrangement, and in machines with a vertical two-tier arrangement of barrels, the gates of one vertical row were rotated 180 ° relative to the gates of the other row. The shutters of the 1st, 2nd and 3rd variants were longitudinally sliding piston, the rear part of the shutter, which received an additional speed at the moment the shutter was unlocked, served as an accelerator. In the fourth version – vertical wedge gates.
The anti-recoil devices for all variants of anti-aircraft guns consisted of spring recoil pads and hydraulic recoil brakes. All guns have intermittent power supply. In the first version, food was produced from a common clip for two volleys, in the second version – a common magazine for 4 – 6 volleys, in the third version – a separate magazine for each barrel with a capacity of 20 rounds, in the fourth version – a common magazine with a capacity of 8 – 10 rounds.In the first and third options, the magazine was fed by one loader, and in the second and fourth options, two loaders were required at once to feed one magazine. A significant and main disadvantage of these 8-barreled anti-aircraft guns was the failure of the entire installation with a delay in firing one machine gun. Therefore, the Germans chose for these guns an automatic scheme with a long recoil of the barrel, which gave the minimum number of delays. In turn, the long rollback of the barrel reduced the rate of fire of the machine gun compared to the scheme with a short rollback of the barrel.The rate of fire of one machine gun was 420 – 480 rounds per minute, and the entire system was 3360 – 3840 rounds per minute. The maximum reach in height was 2200 m, and in the horizon – 4800 m. 20mm unitary rounds were used from the standard 2cm Flak 30 and Flak 38 cannons.
In total, 9 types of projectiles were used, the main of which were fragmentation tracer, armor-piercing tracer and armor-piercing subcaliber. The first three versions of the guns were mounted on experimental carriages, and for the installation of the fourth version, a standard four -barrel carriage from a 37-mm anti-aircraft gun from a 37-mm Flak 38 anti-aircraft gun was used. All four 8-barreled experimental anti-aircraft guns SMK-18 V1 captured by the Red Army as a trophy at the end of World War II, in the post-war period, they were carefully studied in the Soviet artillery design bureaus.