| nkm wz. 38 FK | |
|---|---|
 The gun inlight infantry configuration | |
| Type | Anti-air andanti-tankheavy machine gun/autocannon |
| Place of origin | Poland |
| Service history | |
| In service | 1938–1939 |
| Used by | Poland |
| Wars | World War II |
| Production history | |
| Designer | Wawrzyniec Lewandowski |
| Designed | 1938 |
| Manufacturer | Państwowa Fabryka Karabinów |
| Unit cost | zl30,000 (tank version)[1] |
| Produced | 1938–1939 |
| No. built | 55 |
| Specifications | |
| Mass | 57.6 kilograms (127 lb) |
| Length | 2,015 millimetres (79.3 in) |
| Barrel length | 1,476 millimetres (58.1 in) |
| Width | 202.5 millimetres (7.97 in) |
| Crew | 3 (PL 20A mount)/ 6 (PL 20B mount) |
| Shell | 20x138mmB |
| Shell weight | 320g |
| Caliber | 20 mm |
| Action | blowback |
| Rate of fire | 320-350 rpm |
| Muzzle velocity | 856 metres per second (2,810 ft/s) |
| Effective firing range | 5,000 metres (5,500 yd)/7,000 metres (7,700 yd) |
| Feed system | box(5/10 rounds)/drum(15/100 rounds) |
Thenkm wz. 38 FK (Polish military acronym meaningheaviest machine gun pattern 1938) was a20 mmheavy machine gun (autocannon by modern terminology) produced in inter-warPoland. It was used both inanti-air andanti-tank role and was also adapted fortank use and mounted on someTKStankettes. Mass-produced since 1938, it was used extensively during thePolish Defensive War of 1939.
In line with other arms design of the time, the nkm wz. 38 FK was a code-name rather than a proper name of the weapon. The nkm acronym stands forPolish:najcięższy karabin maszynowy, literallythe heaviest machine gun (i.e. heavier than standard contemporaryheavy machine guns using standard rifle cartridges such as the 7.92 Mauser,.303 British or 7.62×54mmR). The second part of the name,wz. 38 stands forPolish:wzór 38, that is Mark 1938, referring to the year the weapon was submitted to the military for testing or the year the weapon was designed. Finally, when more than one weapon of certain type was conceived in the same year, additional designation was added at the end to differentiate between various types. In this case theFK stood forFabryka Karabinów, the Warsaw-based state-owned rifle factory.
In early 1930s thePolish Army was looking for a modern anti-tank and anti-air weapon to replace outdated World War I equipment still in use. In 1931heavy machine guns made byHotchkiss,Solothurn andOerlikon were tested, but were found unsuitable for Polish needs. Most importantly, they could not suit both AT and AA roles well. In 1937 another commission was sent abroad to test the newly designed weapons of20mm calibre byOerlikon,Madsen andHispano-Suiza. As all designs had several flaws, it was decided to start works on an indigenous design. EngineerBolesław Jurek of Warsaw-basedFabryka Karabinów company became the lead designer.[2]
Four designs were considered for the wz 38FK, dubbed Models A-D, from which only the Model A would become adopted;
Model A -heavy machine gun designed byBolesław Jurek. Adopted by thePolish Army in 1939. Automatic self-repeating weapon. Operating on the principle of short barrel recoil. It had an easily replaceable barrel with a muzzle brake. It is fed from a box magazine with a capacity of 5 or 10 rounds or a drum magazine with a capacity of 15 rounds. It is mounted in the tank with a spherical yoke with an armored cover developed by Napiórkowski and Miniewski.
Model B - prototype of aheavy machine gun developed byW. Lewandowski. A gas operated design which utilised a gas port in the barrel. Fed from a cloth or metal link belt or from a box magazine.
Model C - prototype of aheavy machine gun developed byS. Rytwiński andW. Lewandowski. Operation as the Model B HMG. Fed via 200 round cloth or metallic belt, box magazine for 5-10 rounds or drum magazine with capacity of 100 rounds. A PL20A tripod base was designed for the use of the gun as an anti-tank infantry weapon. The tripod was made according toJ. Skrzypiński's design and developed byL.Kowalewicz. In this version, the HMG was to be equipped with a lighter barrel and 5 round box magazine. A heavier PC20A wheeled mount would be used for the weapon when equipped at higher tactical levels.The mount had a weight of 400–500 kg and was developed by L. Kowalewicz. It was predicted that the HMG could be used for arming aircraft.
Model D - prototypeheavy machine gun developed by Bolesław Jurek. Works like Model B. Powered by a 100-round drum magazine. Could be used for arming aircraft.[2]
A first batch of 100 Model A HMGs was ordered on August 26, 1938. The gun was produced bySanok-based Zieleniewski company, with barrels made byPruszków-basedZakłady Przemysłowe Stowarzyszenia Mechaników Polskich z Ameryki works and newly designed ammunition at the State Munition Works inSkarżysko-Kamienna. In April 1939 another 140 pieces were ordered, 40 of those as stationary weapons (without mountings) and with time the production was to reach 100 pieces a month.[2]
However, the initial costs were high. The design itself, factory equipment and the guns of the first batch themselves cost roughly 2.2 millionzłotys. The plans forbudget year 1939/1940 amounted to almost 3.4 million. In addition, the initial batch was being manufactured at a much slower rate than expected. Because of that by the outbreak ofWorld War II out of 896 pieces ordered for delivery by 1940 only 55 pieces were delivered to thePolish Army.[2]
The nkm wz. 38 FK was accepted by the Polish Army in 1939. As a stop-gap solution roughly 30TK-3 andTKStankettes were rearmed with this HMG. As an anti-tank and anti-air weapon, the gun was to be used extensively: 8 pieces in AA configuration for everyinfantry division.
However, as of September 1, 1939 the overall production did not exceed 60 pieces.
| Distance (m) | Thickness (mm) |
| Hardened Steel | |
| 100 | 20 |
| 200 | 18 |
| 300 | 17 |
| 400 | 15 |
| 500 | 13 |
| Steel | |
| 300 | 25 |
| 400 | 23 |
| 500 | 20 |
Note: Capable of penetrating any German tank of 1939 except for possiblyPanzer IV. The more recently provided photos show that the tank driven by PrinceWiktor IV Albrecht von Ratibor, destroyed by Mr. CadetRoman Orlik, was indeed a Panzer IV and not aPanzer 35(t).[citation needed]