152-mm gun-howitzer M1937 (ML-20)

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152-mm howitzer-gun model 1937 (ML-20)

ML-20 in Hämeenlinna artillery Museum, Finland.
Type howitzer-gun
Place of origin USSR
Production history
Produced 1937-1947
Number built 6,884
Specifications
Weight combat: 7,270 kg
travel: 7,930 kg
Length 8.18 m (with limber; barrel pulled back)
Barrel length bore: 4,240 mm / 27.9 calibers
overall: 4,412 m / 29 calibers (without muzzle brake)
Width 2.35 m
Height 2.27 m
Caliber 152,4 mm
Breech interrupted screw
Recoil hydropneumatic
Carriage split trail
Elevation -2° to 65°
Traverse: 58°
Rate of fire 3-4 rounds per minute
Maximum range 17,23 km

The 152-mm howitzer-gun model 1937 (ML-20), was a Soviet gun-howitzer. The gun was successfully used in the World War II, remained in service for a long time after the end of the war and saw action in many other wars and conflicts of mid and late 20-th century.

Contents

[edit] Description

The ML-20 was officially classified as howitzer-gun, i.e. an artillery system which combines characteritics of a howitzer and (to lesser extent) of a gun and therefore can be used in both roles. This universality was achieved by wide range of elevation angles and by using separate loading with 13 different propellant loads. The gun was fitted with both telescopic sight for direct fire and panoramic sight for an indirect one. For ballistic calculations and meteorological corrections a special mechanical device was developed. The device, called meteoballistic summator, consisted of a specialized slide rule and a pre-calculated table. After World War II similar devices were introduced for other types of guns.

The barrel was either monoblock or assembled. Some sources indicate that a third type - with free tube - also existed. To soften a recoil, a large slotted muzzle brake was fitted. The breechblock was of interrupted screw type, with forced extraction of cartridge during opening. A safety lock prevented opening of the breechblock before the shot; if there was a need to remove a shell, the lock had to be disabled. To assist loading when the barrel was set to high elevation angle, the breach was equipped with cartridge holding mechanism. The gun was fired by pulling a trigger cord.

The recoil system consisted of hydraulic buffer and hydropneumatic recuperator. Each held 22 litres of liquid. A pressure in the recuperator reached 45 atm.

The carriage was of split trail type, with shield and balancing mechanism. It had leaf spring suspension and steel wheels with rubber tires. During transportation the barrel was usually pulled back. The gun could also be towed with the barrel in its normal position, but in this case the transportation speed was limited, about 4-5 km/h (compared to 20 km/h with barrel pulled back). The gun could be set up for combat in 8-10 minutes. The carriage, designated 52-L-504A, was also used in the 122-mm gun model 1931/37 (A-19).

[edit] Development history

Among other artillery pieces the Red Army (RKKA) inherited from the Imperial Russian Army a 152-mm siege gun M1910, developed by Schneider. The gun was modernized twice in 1930s, resulting in 152-mm gun M1910/30 and 152-mm gun M1910/34. However, its mobility, maximum elevation and speed of traverse still needed improvement. In 1935-36 the Plant No. 172 (the Perm Plant) in Motovilikha tried to continue the modernization works, but the Main Artillery Directorate (GAU) insisted on more significant upgrade.

Consequently, the design bureau of the plant developed two guns ML-15 and ML-20. While the former project was initiated by GAU, the latter started as private development; the team working on it was led by F. F. Petrov. Both guns used barrel and recoil system of the M1910/34. The ML-20 also inherithed from the older gun its wheels, suspension and trails.

The ML-15 reached ground tests in April 1936, was returned for revision and was tested again in March 1937, this time successfully. The ML-20 went through ground tests in December 1936 and through army tests next year. After some defects (mostly in carriage) were eliminated, the ML-20 was recommended for production and on 22 September 1937 it was adopted as 152-mm howitzer-gun model 1937 (Russian: 152-мм гаубица-пушка образца 1937 года (МЛ-20)).

It is not clear why the ML-20 was preferred. The ML-15 was lighter (about 500 kg less in combat position, 600 kg in travelling position) and more mobile (maximum transportation speed 45 km/h). On the negative side, the ML-15 had more sophisticated carriage (however, the final version of the ML-20 carriage incorporated some features of the ML-15). Some sources claim that the choice was made because of the economic factor - the ML-20 was more similar to the M1910/34, meaning less arrangements for production.

[edit] Production history

The gun was in production in 1937-46. 6,884 guns were manufactured and about 4,000 ML-20S barrels for using in self-propelled guns SU-152 and ISU-152. The ML-20 was eventually replaced by the D-20 152 mm gun with identical ballistics, which entered production in 1956.

Production of МL-20s, pcs. [1]
Year 1937 1938 1939 1940 1941 1942 1943 1944 1945 1946 Total
Produced, pcs. 148 500 567 901 1,342 1,809 1,002 275 325 15 6,884

Smaller production rates toward the end of the war were caused by two reasons. First, most of the barrels produced in these years were ML-20S. Second, after Germans fielded heavy tanks the plant was ordered to increase production of A-19 122 mm guns instead of some ML-20.

[edit] Organization and employment

ML-20 in Poznań Citadel, Poland.
ML-20 in Poznań Citadel, Poland.
ML-20 in Hämeenlinna Artillery Museum, Finland.
ML-20 in Hämeenlinna Artillery Museum, Finland.
ML-20 in Hämeenlinna Artillery Museum, Finland.
ML-20 in Hämeenlinna Artillery Museum, Finland.
ML-20 in Batey ha-Osef Museum, Israel.
ML-20 in Batey ha-Osef Museum, Israel.

[edit] Red Army

The ML-20 was originally intended for corps artillery. Together with the 122-mm gun A-19 it formed a so-called "corps duplex". In 1940-41 there were three types of corps artillery regiments:

  • With two battalions of ML-20 and one of either A-19 or 107-mm guns (a total of 24 ML-20s).
  • With two battalions of ML-20 and two of either A-19 or 107-mm guns (a total of 24 ML-20s).
  • With three battalions of ML-20 (a total of 36 ML-20s).

Soon after the outbreak of the Great Patriotic War the corps artillery was eliminated (as rifle corps themselves were eliminated). It was restored later in the war. The new corps artillery regiments were supposed to be armed with 122-mm guns or 152-mm howitzers, but some memoirs mention that the ML-20 was also used.

From 1943 the gun was employed by artillery regiments of armies. Such regiment had 18 ML-20s. Guard armies from early 1945 had artillery brigade with 36 ML-20s.

The ML-20 also used by artillery regiments (24 pieces) and brigades (36 pieces) of the Reserve of the Main Command.

It was primarily used for indirect fire againf enemy personnel, fortifications and key objects in the near rear. Heavy fragments of the OF-540 HE-Fragmentation shell were capable of piercing armour up to 20-30 mm thick, making a barrage dangerous to thinly armored vehicles and to some extent to heavier armoured ones as the fragments could damage chassis, sights or other elements; sometimes a close expolsion caused damage inside a vehicle even though the armour remained intact. Direct hit of a shell often resulted in tearing away a turret of a medium tank or jamming it in case of a heavy tank.

The gun was also equipped with armour-piercing shells for direct fire against armoured targets. Although not an ideal anti-tank gun because of its large size, slow traverse and slow rate of fire, in 1943 the ML-20 was one of a few guns effective against new German tanks. For example, the glacis armour of the heavy Tiger I could be penetrated from about a kilometer.

In addition to being used in all significant operations of the Red Army in Great Patriotic War, the gun saw combat in the Winter War against the Mannerheim Line fortifications.

Excellent characteristics of the gun, including reliability and ease of maintenance, allowed it to remain in service with the Soviet Army for a long time after the war.

[edit] Other operators

In the early stage of the Great Patriotic War hundreds of ML-20 were captured by Wehrmacht. The gun was adopted by Germans as 15,2 cm KH.433/1(r). From February 1943 Germans manufactured an ammunition for the gun.

The Finnish Army captured 37 guns of the type in 1941-44 and received additional 27 from Germany. These guns were adopted as 152 H/37. While the gun was generally liked, the Finnish Army didn't possess enough prime movers suitable for towing such a massive piece. As a result, some of the guns were assigned to coastal artillery. Two pieces were captured back by the Red Army. A number of modernized guns still remain in reserve.

After the war the ML-20 was widely exported to Warsaw Pact allies and to many states in Asia and Africa (in some of those states the gun still remains in service). It was adopted by Egypt and Syria and therefore saw action in Arab-Israeli conflict. In 2002 a TV documentary featured ML-20 employed by the Afghan Northern Alliance forces against the Taliban fighters; it seems likely that the guns were initially supplied to the Najibullah's regime.

[edit] Variants

The barrel was manufactured in two variants - monoblock or assembled. Some sources indicate that a third type - with free tube - also existed.

Except the basic variant, the only variant to reach mass production was the ML-20S, developed for use in self-propelled guns, with differently placed controls for easier operation in small enclosed compartment.

  • ML-20 with powder bag loading - In 1937 the Main Artillery Department decided - for economic reasons - to modify medium caliber guns to use powder bag loading instead of cartridge loading. An experimental ML-20 piece was built in 1939; the trials were unsuccessful.
  • ML-20SM - Modified ML-20S with identical ballistics. Muzzle brake was removed. The gun was mounted in the experimental ISU-152 model 1945, of which only one unit was built.
  • BL-20 - ML-20 with cast breech and wedge breechblock. Was developed by OKB-172 (sharashka of the NKVD) in 1946.
  • ML-20 with M-46-type carriage - ML-20 with a modified carriage, resembling in construction a carriage of the M-46 130 mm gun. In 1950 an experimental piece was built and tested.

[edit] Summary

The ML-20 was one of the most successful Soviet artillery pieces of World War II. Its characteristics positioned it between classical short-range howitzers and special long-range guns. Compared to the former, the ML-20 has better range (e.g. the German 15 cm sFH 18 had range of 13.3 km), which often allowed it to shell positions of enemy artillery while remaining immune to enemy fire. Its advantage over the latter was in weight and cost, and therefore in mobility and production rate. For example, the German 15 cm K.18 with range of 24.8 km weighed 12.5 tons and only 101 pieces were built; of the excellent 17 cm K.18 Mrs.Laf (23,4 t, 29,6 km) 338 pieces were manufactured; lighter 10,5 cm K.18 (5,6 t, 19,1 km) was more common (2,135 pieces) but its 15 kg shell was much less powerful than a 44 kg shell of ML-20. German attempts to produce an analogue to the ML-20 were unsuccessful. The 15 cm s.F.H.40 were never produced due to construction defects; the 15 сm s.F.H.42 had insufficient range and only 46 pieces were built. In 1943 and 1944 Wehrmacht announced requirements for a 15 cm howitzer with a range of 18 km, but none reached production.

Of other guns with more or less similar characteristics, there were French 155 mm guns model 1917 and 1918 with longer range, but some 3.5 tons heavier. The Czechoslovakian howitzer K4 (used by Germans as 15 cm s.F.H.37(t)) was about 2 tons lighter, but with range more than 2 km shorter and only 178 pieces were built. The British BL 5.5 inch (140 mm) gun also had shorter range.

Main shortcomings of the ML-20 were its weight and limited mobility. As the experience of the ML-15 project suggests, the gun could be made somewhat lighter and more suitable for high-speed transportation. Use of a muzzle brake can be seen as minor flaw: while softening a recoil and thus allowing to use lighter carrige, muzzle brake has a disadvantage of redirecting some of the gases that escape the barrel toward the ground, where they raise dust, revealing the gun position. But when the ML-20 was developed muzzle brake was already a common element in artillery pieces of that class.

[edit] Ammunition

Available ammunition [2]
Type Model Weight, kg HE weight, kg Muzzle velocity, m/s Range, m
Armor piercing shells
APHE BR-540 48,8 0,66 600 4,000
APBC (from late 1944) BR-540B 46,5 0,48 600 4,000
Naval semi-AP model 1915/28 51,07 3,2 573
HEAT BP-540 27,44 680 3,000
Anti-concrete shells
Anti-concrete howitzer shell G-530 / G-530Sh 40,0 5,1
Anti-concrete gun shell G-545 56,0 4,2
High explosive and fragmentation shells
Gun shells
HE-Fragmentation, steel OF-540 43,6 5,9-6,25 655 17,230
HE-Fragmentation, steel OF-540Zh 43,6 5,9-6,25
HE, old F-542 38,1 5,86
HE, old F-542G 38,52 5,83
HE, old F-542ShG 41,0 5,93
HE, old F-542Sh 40,6 6,06
HE, old F-542ShU 40,86 5,96
HE, old F-542U 38,36 5,77
Howitzer shells
HE-Fragmentation, steel OF-530 40,0 5,47-6,86
HE-Fragmentation, steely iron OF-530A 40,0 5,66
HE, old F-533 40,41 8,0
HE, old F-533K 40,68 7,3
HE, old F-533N 41,0 7,3
HE, old F-533U 40,8 8,8
HE, steely iron, old French F-534F 41,1 3,9
HE for 152-mm mortar model 1931 F-521 41,7 7,7
HE, British, for Vickers 152-mm howitzer F-531 44,91 5,7
Shrapnel shells
Shrapnel with 45 sec. tube Sh-501 41,16-41,83 0,5 (680—690 bullets)
Shrapnel with Т-6 tube Sh-501T 41,16 0,5 (680—690 bullets)
Illumination shells
Illumination, 40 sec. S 1 40,2
Chemical shells
Fragmentation-chemical gun shell OH-540
Chemical howitzer shell HS-530 38,8
Chemical howitzer shell HN-530 39,1
Chemical (post-war) ZHZ
 
Armour penetration table[3]
APHE shell BR-540
Distance, m Meet angle 60°, mm Meet angle 90°, mm
500 105 125
1000 95 115
1500 85 105
2000 75 90
APBC shell BR-540B
Distance, m Meet angle 60°, mm Meet angle 90°, mm
500 105 130
1000 100 120
1500 95 115
2000 85 105
Naval semi-AP model 1915/28
Distance, m Meet angle 60°, mm Meet angle 90°, mm
100 110 136
500 104 128
1000 97 119
1500 91 111
2000 85 105
These data was obtained by Soviet methodics of armour penetration measurement (penetration probability equals 75%).
They are not directly comparable with western data of similar type

[edit] Interesting facts about ML-20

  • On 2 August 1944 the ML-20 howitzer-gun No. 3922 became the first gun to shell German territory in the second half of Great Patriotic War.
  • Loader of the ML-20 had to carry 40 kg shells alone.
  • The 41st artillery brigade - one of the first brigades to be equipped with the ML-20 - after a number of reorganizations became a training center for soldiers and seregants of the Russian Army Missile and Artillery Forces. There is a memorial ML-20 piece in one of the center's parks.
  • A small number of operational ML-20 howitzer-guns is still present in the Russian Army ordnance depots.
  • 152 mm HE-Frag projectiles OF-540, initially developed for the ML-20, are still in Russian Army service and can be fired from modern 152 mm ordnance pieces.
  • ML-20 howitzer-guns were towed by heavy artillery tractors Voroshilovetz and Komintern; these vehicles produced by the same Kharkov locomotive plant that developed the T-34 tank and were equipped with the same V-2 diesel engine.

[edit] Surviving pieces

ML-20 guns in Saint Petersburg.
ML-20 guns in Saint Petersburg.

ML-20s are on display in a number of military museums. Among other places, the gun can be seen:

[edit] Notes

  1. ^ Shirokorad A. B. - Encyclopedia of the Soviet Artillery
  2. ^ Shirokorad A. B. - Encyclopedia of the Soviet Artillery
  3. ^ Shirokorad A. B. - Encyclopedia of the Soviet Artillery

[edit] References

Wikimedia Commons has media related to:
  • Shirokorad A. B. - Encyclopedia of the Soviet Artillery - Mn. Harvest, 2000 (Широкорад А. Б. Энциклопедия отечественной артиллерии. — Мн.: Харвест, 2000., ISBN 985-433-703-0)
  • Shirokorad A. B. - The God of War of The Third Reich - M. AST, 2002 (Широкорад А. Б. - Бог войны Третьего рейха. — М.,ООО Издательство АСТ, 2002., ISBN 5-17-015302-3)
  • Ivanov A. - Artillery of the USSR in Second World War - SPb Neva, 2003 (Иванов А. Артиллерия СССР во Второй Мировой войне. — СПб., Издательский дом Нева, 2003., ISBN 5-7654-2731-6)
  • Shunkov V. N. - The Weapons of the Red Army, Mn. Harvest, 1999 (Шунков В. Н. - Оружие Красной Армии. — Мн.: Харвест, 1999.) ISBN 985-433-469-4
  • Zheltov I. G., Pavlov I. V., Pavlov M. V., Solyankin A. G. - Soviet Medium Self-propelled Artillery 1941-1945 - M. Exprint, 2005 (Желтов И. Г., Павлов И. В., Павлов М. В., Солянкин А. Г. - Советские средние самоходные артиллерийские установки 1941—1945 гг. — М.: ООО Издательский центр «Экспринт», 2005. — 48 с. ISBN 5-94038-079-4)

[edit] External links

Soviet Artillery of Great Patriotic War
Anti-tank guns
37-mm gun 1-K | 45-mm gun M1937 | 45-mm gun M-42 | 57-mm gun ZiS-2 | 100-mm gun BS-3
Mountain guns
76-mm mountain gun M1938
Regimental guns
76-mm gun M1927 | 76-mm gun M1943
Divisional guns
76-mm gun M1902/30 | 76-mm gun F-22 | 76-mm gun USV | 76-mm gun ZiS-3
122-mm howitzer M1909/37 | 122-mm howitzer M1910/30 | 122-mm howitzer M-30
Corps and Army level guns
122-mm gun A-19 | 152-mm howitzer M1909/30 | 152-mm howitzer M1910/37
152-mm howitzer M-10 | 152-mm howitzer D-1 | 152-mm gun M1910/30
152-mm gun M1910/34 | 152-mm gun-howitzer ML-20
Very heavy guns
152-mm gun M1935 | 203-mm howitzer B-4 | 210-mm gun M1939
280-mm mortar M1939 | 305-mm howitzer M1939
Air defense guns
25-mm gun 72-K | 37-mm gun 61-K | 76-mm gun M1938 | 85-mm gun 52-K

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