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M1937 (ML-20) 152 mm howitzer-gun

The Soviet Army field artillery masterpiece M-1937 was given the nickname of the `Kill` beast. In the Second World War ML- 20 had no rival. By comparison, the German howitzer "15 cm sFH 18" had a range of 13.3 km. German howitzers had inferior characteristics. The ML-20 came out many times from under enemy artillery that it could strike at the same time.

The ML-20 howitzer cannon was designed and built by the office headed by FF Petrov from the Soviet factory no. 172, "Motovilikha" for the replacement of the old model 1910/34 152 mm horse howitzer, made together with the company "Schneider". It was produced between 1937-1946 in about 6,800 copies and enjoyed great success being superior to most similar Western models. During World War II it equipped Soviet artillery and army corps and remained in stock until it was replaced by the M-46 130 mm cannon in 1954 and with the D-20 howitzer cannon, starting with 1956.

In 1934, the Red Army was armed with a 152-mm howitzer, which had a number of disadvantages:

• Only the carriage was sprung, but the front end was not, so the transport speed was limited to 18-20 km / h.
• The suspension was turned off by a special mechanism, and not automatically, which took 2-3 minutes.
• The upper machine was too complex a casting.
• And the most serious drawback was the combination of the lifting and balancing mechanism in one system.
• Finally, although the 1934 system was called a howitzer, its elevation angle (+45) was too small for howitzers.

In 1935-1936, a group of designers of plant No. 172 (Perm plant) carried out work on the overhaul of the 152-mm howitzer mod. 1934 In particular, its elevation angle was increased to +62. For unknown reasons, the Artillery Directorate ordered the project to be terminated.

The 152-mm howitzer-gun ML-20 was designed in parallel with the ML-15 in the design bureau of plant No. 172 under the direction of FF Petrov. It is interesting that work on the ML-20 was started by the plant on its own initiative, and the ML-15 was developed by order of the Main Artillery Directorate.

Two other groups of designers of plant # 172 designed two versions of a new artillery system, which was called the "cannon howitzer", that is, a universal artillery system, which had more howitzer properties and fewer cannon-based ones. The first version of the howitzer-gun received the ML-15 index, and the second ML-20 (ML index of the plant, from the name Motovilikha - a village near Perm, where the plant is located). The barrel and bolt of the ML-15 and ML-20 are identical to the arr. 1934 The cradle and recoil devices in the ML-15 and ML-20 are mostly taken without changes from the arr. 1934, except that the ML-20 trunnion clip consisted of two halves, while the ML-15 was one whole.

he first model of the ML-15 was manufactured by the plant number 172 at the beginning of 1936 and after factory tests on April 29 was sent to NIAP. By June 1936, the field tests were completed. The commission found them unsatisfactory. After that, the Artillery Directorate ordered two ML-15s to plant No. 172 with changes based on the test results. In particular, the combat axle was moved forward by 180 mm, which reduced the pressure on the trunk. The lifting mechanism was changed instead of two sectors, one was introduced, then instead of one guidance speed there were two. Both systems were completed in late 1936 and factory tested. From February 10 to March 20, 1937, field tests of the modernized ML-15 system were carried out at NIAP. 113 shots were fired and the system was transported at a speed of 30-45 km / h. There were no comments on the system. However, the tests were suddenly interrupted according to the order of the head of the Research Department of the Artillery Directorate Zheleznyakov. In June-July 1937, the ML-15 was fired again, charges were picked up for it, etc. However, the ML-20 was still put into service. In general, the ML-15 was clearly better than the ML-20. Why then did they not accept ML-15? Yes, just because the ML-15 was a completely new design, and in order to start producing it, you need to rebuild the production base. And, since the ML-20 was already the best artillery system in the world, they decided to increase their number. The ML-20 was classified as a howitzer due to the combination of common features obtained by a very large vertical firing range (-2° to 65°) as well as the use of different propelling loads, grouped into 13 subloads. For the calculation of ballistic and weather corrections, a special device called a "meteorological summator" was created, consisting of a calculation ruler and pre-calculated tables, a system that was used after the war and in other Soviet guns.

Due to the relatively high weight, respectively 7,930 kg, the affect was completed with an anti-train, together being towed by crawler tractors of type "Voroshilovets" and "Komintern". These tractors were produced at the Kharkov locomotive plant, The affect was named 52-L-504 A and is the one used by the A-19 cannon, cal. 122 mm, model 1931/37. During transport, the barrel could be kept in the normal position, in which case the travel speed was 4-5 km / h or it could be retracted backwards on the jaw support, in which case the speed increased to 20 km / h. The transition from the fighting position, to the marching position and vice versa was done in about 8-10 minutes.

In order to increase the speed of travel in rough terrain and to overcome some hard to reach areas, the barrel could be dismantled and transported on the barrel carriage. The barrels were of two types, monobloc or with removable tube equipped with a recoil brake which had a small disadvantage. During the firing, due to the circular holes, the gas jet raised dust in front of the howitzer. The elements that distinguished the howitzer from other guns were the two large balancers that exceeded the height of the shield and that were also found in the horse cannon. 122 mm, same model. The lock was of the screw type, with a device against accidental opening while the howitzer was loaded, and for large angles of inclination of the barrel, the butt had a device to facilitate loading. For direct aiming, as a cannon, there was an optical booster in the batch.

The target effect of the ammunition was very strong, enhanced by the high weight of the basic explosive projectile, OF 540 of 43.6 kg. The projectiles were completed with RGM 2 warheads for percussive firing and D 1 U warheads for fuse firing. The shrapnel from this projectile could pierce 20-30 mm armor, and a direct blow often dislodged the turret of medium-sized German tanks or damaged heavy ones. Although large height advantage in the battle do not have lot antitank ammunition and projectiles that can pierce armor penetrating the German Tiger tank (25 to 120 mm) at a distance of 1,000 m.

The artillery regiment was deployed directly under the headquarters, and field artillery fire support masterpiece was active in the distance. A distinctive feature of the ML-20 is a unique combination of different angles of elevation and initial velocity of the projectile, which are given a choice of one of the thirteen propellants, some providing a range of over 17 kilometers. As a result of gun could be used as a howitzer, mounted on a shooting trajectory with a relatively low velocity of the projectile, and a gun - on flat trajectory at a high speed projectile.

Production of ML-20 was carried out only on the factory number 172 in Perm from 1937 to 1946. Striking power utilizing the large diameter 152mm gun been adopted as a self-propelled artillery gun as the SU-152/ISU-152. In addition to the release of towed guns were fired about 4,000 barrels ML-20S to be mounted on self-propelled gun (SPG) SU-152 and ISU-152 (a total built 3242 ISU-152 self-propelled guns and about 670 self-propelled guns SU-152, the exact number varies from various sources). Successor ML-20 was the 152-mm gun-howitzer D-20, which was in serial production since 1956. This instrument was identical with the ML-20 ballistics.

The ML-20 was, by far, the best instrument, as evidenced by the duration of its serial production and service. It was in a niche between the classical field howitzer with a short barrel and long-barreled guns special power, strongly outperforming the first in the firing range, and in the second by weight (as a consequence of this, it had better mobility and lower cost). In practice, the first advantage led to the fact that the ML-20 was able to strike at the positions of the most common enemy howitzers, firing from the reach of those distances (for example, the most common German howitzer 15 cm sFH18 had a maximum range of 13.3 km). The second advantage is the result of a much greater number of issued ML-20 compared with the number of guns produced high power, which were much more expensive.

The Germans repeatedly tried to create an instrument with similar characteristics to the ML-20, but failed. Howitzer 15 cm sFH40 did not go into mass production because of a number of structural deficiencies; another design, 15 cm sFH42, had a maximum firing range of 15,100 meters and was released in an amount of 46 units. In 1943 and 1944 the Wehrmacht announced tenders for the creation of a new 15-cm howitzers with a range of 18 km, but German designers failed to create adesign suitable for mass production. The English 5.5-inch (140 mm caliber) field gun, which was launched into production in 1941, with a firing range of 14 km, had only a slight edge over the 15 cm sFH18 and was inferior ML-20 in this indicator.

The German howitzer "15 cm sFH 40" was produced with defects and the model "15 cm sFH 42" had a smaller beat being produced in only 46 copies. A similar howitzer was the French "Filloux", cal. 155 mm with a range of 19 km but with a very high weight of 13 tons. One howitzer approaching the ML-20 was the "Skoda" howitzer, which was also equipped by our army, 2 tons lighter but 2 km smaller. The British BL-5.5 inch (140 mm) howitzer also had a smaller beat. On August 2, 1944, the 3,922 series howitzer was the first muzzle to hit German territory in World War II.

It endowed all the states of the Warsaw Pact, in the Middle East (Syria and Egypt) as well as with the endowment of some Asian states. The Finnish army captured a number of 37 howitzers and received another 21 pieces from the German army, which it modernized and used, including for coastal artillery, by 2007. In conclusion, the ML-20 howitzer cannon was one of the best artillery pieces of World War II. Attempts by the Germans to achieve a similar model failed. For example, the howitzer "15 cm K 18" with a range of 24.8 km and a weight of 12.8 tons of which only 101 pieces were built.

The Romanian Army bought it in 1949-1950. In 1956 they were equipped as follows: in the general-strategic reserve at the 32nd Independent Cannon Brigade where there were 9 batteries x 4 howitzers in 3 mixed divisions, together with horse cannons. 130 mm; at the Military Region no. 3 (the equivalent of the army echelon that had been disbanded) at the 54th Cannon Regiment from Floresti: 2 divisions x 3 batteries x 4 howitzer guns. They were also provided to the 182nd Lugoj Artillery Regiment from the 40th Army Corps: 3 divisions x 3 batteries x 4 howitzers, these being replaced with horse howitzers. 150 "Skoda". At the same time, the ISU 152 self-propelled howitzer was used in our army, which used the barrel and ammunition of the ML-20 howitzer cannon.

The drawbacks of ML-20 included a large mass and limited speed of carriage, which was due to conservative design. With the experience of the ML-15, the gun could be constructed easier and more mobile. For transporting tools a powerful tractor was needed, which in the Great Patriotic War were relatively few in number. For transportation ML-20 used heavy tracked artillery tractors "Voroshilovets" and "Comintern" , which were issued by the Kharkiv Locomotive Works - designer and first manufacturer of the famous tank T-34. This shortcoming was noted, and insufficient mobility led to the conclusion of the corps artillery guns to higher organizational levels in the hierarchy - the Army artillery or artillery RVGK.

Another disadvantage was the the construction of the ML-20 muzzle brake. This caused unmasking the gun when shooting, as flowing out of the barrel after the departure of the projectile propellant gases change direction after passing through the muzzle brake and raised a cloud of dust from the ground. This fact was particularly important when shooting at small angles of elevation, to combat this undesirable phenomenon is sometimes applied wetting of the underlying surface water. On the other hand, use of a muzzle brake at the time has already become a common practice for this class of implements.