152 mm howitzer-gun M1937 (ML-20)

Infobox Weapon
name=152 mm howitzer-gun M1937 (ML-20)


caption=ML-20 in Hämeenlinna artillery Museum, Finland.
origin=USSR
type=howitzer-gun
is_ranged=
is_bladed=
is_explosive=
is_artillery=yes
is_vehicle=
is_UK=
service=
used_by=
wars=
designer=Design bureau of No. 172 Plant,
headed by F. F. Petrov
design_date=
manufacturer=
production_date=1937–1947
number=6,884
variants=
weight=combat: 7,270 kg
(16,027 lbs)
travel: 7,930 kg
(17,482 lbs)
length=8.18 m (27 ft) (with limber; barrel pulled back)
part_length=bore: 4,240 mm / 27.9 calibers
overall: 4,412 m / 29 calibers (without muzzle brake)
width=2.35 m (7.70 ft)
height=2.27 m (7.40 ft)
crew=
cartridge=
caliber=152.4 mm (6 in)
action=
rate=3-4 rounds per minute
velocity=
range=
max_range=17.23 km (10.7 mi)
feed=
sights=
breech=interrupted screw
recoil=hydropneumatic
carriage=split trail
elevation=-2° to 65°
traverse=58°
blade_type=
hilt_type=
sheath_type=
head_type=
haft_type=
diameter=
filling=
filling_weight=
detonation=
yield=
armour=
primary_armament=
secondary_armament=
engine=
engine_power=
pw_ratio=
suspension=
vehicle_range=
speed=

The 152 mm howitzer-gun M1937 (ML-20) ( _ru. 152-мм гаубица-пушка обр. 1937 г. (МЛ-20)), was a Soviet gun-howitzer. The gun was developed by the design bureau of the plant no 172, headed by F. F. Petrov, as a deep upgrade of the 152-mm gun M1910/34, in turn based on the 152-mm siege gun M1910, a pre-World War I design by Schneider. It was in production from 1937 to 1946. The ML-20 saw action in World War II, mainly as a corps / army level artillery piece of the Soviet Army. Captured guns were employed by Wehrmacht and the Finnish Army. Post World War II, the ML-20 saw combat in numerous conflicts during the mid to late twentieth century.

Description

The ML-20 was officially classified as howitzer-gun, i.e. an artillery system which combines characteristics 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 monobloc or built-up. Some sources indicate that a third type - with loose liner - 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 (some early production pieces received spoked wheels with solid tires from M1910/34). 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).

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 No. 172 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 ( _ru. 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.

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.

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.

urviving pieces

ML-20s are on display in a number of military museums. Among other places, the gun can be seen:
*In the Central Armed Forces Museum and at the Poklonnaya Hill, Moscow, Russia.
*In the Museum of Artillery and Engineering Forces, Saint Petersburg, Russia.
*In the Artillery Museum in Hämeenlinna, Finland.
*In the IDF History Museum ("Batey ha-Osef"), Tel Aviv, Israel.
*In Poznań Citadel, Poland.
*In the US Army Ordnance Museum, Aberdeen, Maryland, USA.

Notes

References

*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)
*Kolomiets M. - "The Battle of River Khalkhin-Gol" - "Frontovaya Illustratsiya" magazine, no. 2, 2002 (М.Коломиец. - Бои у реки Халхин-Гол. - журнал «Фронтовая иллюстрация», №2, 2002)
* 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)
** [http://armor.kiev.ua/Tanks/WWII/isu152/1/ A chapter on ISU-152]

External links

* [http://www.jaegerplatoon.net/ARTILLERY6.htm#152H37 Finnish Army 1918-45: Heavy Howitzers at Jaegerplatoon.net]
* [http://www.weltkrieg.ru/artillery/ML-20/ Weltkrieg.ru] ru icon
* [http://www.mil.fi/maavoimat/joukot/tykpr/equip_en.dsp 152 H 88-37 at Mil.fi]