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D-20 / M-55 152-mm Towed Gun-Howitzer
Type-66 152-mm Towed Gun-Howitzer

The D-20 152mm Gun-Howitzer was built shortly after the end of WWII by the F. Petrov Design Bureau in the Soviet Union and was first seen in public during the 1955 May Day parade in Red Square, Moscow. The D-20 is a very large gun, equating to 6-inch caliber, and is heavy for a simple towed carriage. Its restricted mobility, however, is somewhat compensated for by its range of 17,230 meters.

The 152-mm D-20 howitzer cannon and the 122-mm D-74 cannon were created as the so-called "corpus duplex". It was believed that precisely such artillery systems would provide the opportunity to most fully accomplish the tasks facing the corps artillery, while reducing costs and significantly simplify their repair and operation, improve the supply of spare parts and prepare artillery crews.

The D-20, also known as the M1955 or M-55, was the newest 152-mm towed howitzer in the Soviet and Warsaw Pact inventory when first introduced in 1955, replacing the heavier, less powerful, 152-mm gun-howitzer ML-20 (M1937). It is organic to army/front-level artillery and to the artillery regiment/brigade of a tank or combined arms army, while the self-propelled version 2S3 is found in the artillery regiment organic to motorized rifle and tank divisions. The D-20 was exported to all Warsaw Pact armies (except Bulgaria). The Type-66 is a Chinese version, which has been exported to Iraq.

The D-20 uses the same carriage as the 122mm field gun D-74. This short split-trail carriage is distinguished by caster wheels (folded upward for travel) at the end of each trail; a prominent base plate connected to the bottom forward cradle; and a scalloped, winged shield with traveling central portion. The tube, however, differs from that of the D-74inthat it is much shorter (29 versus 47 cal), larger in diameter, and has a larger size double-baffle muzzle brake. Both guns have a two-cylinder recoil mechanism above the tube, and both tubes are prominently stepped, with a semi-automatic, vertically-sliding, wedge breech block. Both guns also fire similar case-type, variable-charge, separate-loading ammunition. The circular firing jack and caster wheels make it possible to rotate the whole gun swiftly through up to 360 degrees. It also has direct fire sights for both day and night and is capable of engaging armored targets with direct fire. It can be towed by truck or armored tractor (AT-L).

The D-20 was the first 152-mm cannon system to incorporate a semiautomatic vertical-sliding-wedge breech block. It fires FRAG-HE, OF-540 with a RGM-2 Fuze Model at a rate of 5-6 rounds per minute with a maximum firing range of 10 miles. Although the ammunition for the system was not changed, modifications allowed a slightly higher rate of fire to be achieved (6 rounds per minute rather than 4), although the sustained rate of fire was unchanged. Because the carriage is based on that of the 122-mm gun D-74, the D-20 cannot be elevated above 45.

D-20 was the first 152-mm gun system with a semi-automatic wedge gate with a vertical movement of the wedge. The barrel of the howitzer D-20 consisted of a pipe, a breech, a holder and a muzzle brake. The shutter is vertical wedge, with mechanical semi-automatic (copy) type. The length of the barrel was 25 calibers. The lifting mechanism has one sector, provides a vertical angle of fire from -5 to +63 degrees.

The rotary mechanism of the screw type, located on the left side of the gun, the angle of horizontal shelling is 58 degrees. At its core, the D-20 is in many ways similar to the earlier model of the 152-mm howitzer D-1, the main difference between the D-20 and the D-1 is the selection of ammunition. From the D-20, it was still possible to shoot most types of D-1 ammunition, the ammunition of which consists of separate loading shots with fragmentation, high-explosive fragmentation and concrete-concrete projectiles. But she had her own family of ammunition. The D-20 was one of the first Soviet artillery systems capable of firing tactical nuclear munitions.

There was also a large selection of chemical munitions, but at present they have all been decommissioned. An improved system of variable power propellant charges allowed to increase the maximum range of the D-20 shot to 17,410 meters, (a VOF-32 shot with a high-explosive fragmentation projectile. The weight of the projectile is 43.56 kg, its explosive charge is 6.88 kg of powerful A-IX explosive -2. Mechanical fuses RGM-2, V-90 and radio-fuse AP-5. At full charge, the initial speed is 655 m / s and the maximum range is 17410 m. Minimum firing range on charge No. 6 4600 m.) And the use of active-reactive projectile allowed to bring the range to 24,000 meters.

One of the latest innovations is the use of a controlled anti-tank projectile guided by a Krasnopol laser beam as part of the 3VOF64 shot. Target illumination is made by advanced artillery observers using 1D15 (PP-3), 1D20, 1D22 or 1D26 instruments. When shooting by Krasnopole, the calculation of three people highlights the target with the help of a laser target indicator-rangefinder included in the portable complex of automated fire control Malachite. Small tank type targets can be highlighted at a distance of up to 5-7 kilometers during the day and 4 km at night, larger targets up to 15 km. Then a guided artillery shell is fired from a remote position.

The D-20 was one of the first Soviet artillery systems capable of firing tactical nuclear weapons. There was also a large selection of chemical munitions (currently decommissioned). An improved system of variable power propellant charges allowed to increase the maximum range of the D-20 shot to 17,410 meters, (a VOF-32 shot with a high-explosive fragmentation projectile. The weight of the projectile is 43.56 kg, its explosive charge is 6.88 kg of powerful A-IX explosive -2 Mechanical fuses RGM-2, B-90 and radio-fuse AR-5.

With a full charge, the initial speed is 655 m / s and the maximum range is 17,410 m. The minimum firing range on a 6m charge is 4,600 m.) And the use of an active-projectile projectile made it possible to bring the firing range to 24,000 meters. In addition, the D-20, as well as a number of other 152-mm artillery systems, include a Centimeter adjustable (controlled) projectile. The index of the complex centimeter 2K24, and the projectile itself - ZOF38. The weight of the projectile is 49.5 kg, the TNT equivalent of BB is 8.5 kg. The firing range from 2 to 12 km. The complex includes a laser target indicator rangefinder (LCD), which is located at a distance of from 0.2 to 5 km from the target. Before the shot, the LCD is aimed at the target. Synchronously with a shot on the LCD signal alert. When the projectile reaches the end of the ballistic trajectory, the laser illumination of the target is turned on. And, when firing a direct fire, the illumination time is limited to one second, and when mounted shooting - three seconds. This is done to prevent the enemy from detecting the radiation source.



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