2A28 Grom

• Name — 2A28 Grom • Origin — Soviet Union • Type — Smoothbore low-pressure cannon • Is Ranged — yes • Is Explosive — yes • Is Artillery — yes • Is Missile — yes • Used By — See BMP-1 Service History • Manufacturer — KBP • Designer — KBP • Design Date — Early 1960s • Production Date — 1966–present • Weight — 115 kg • Length — 1195 mm • Width — 218 mm • Height — 322 mm • Cartridge — PG-15V (HEAT), OG-15V (HE-FRAG), PG-15VN (HEAT-DP) • Caliber — 73 mm • Barrels — 1 • Elevation — -4° to +15° (aimed fire), +33° (maximum non-aimed) • Traverse — 20 °/s horizontal, 6 °/s vertical • Rate — 8 rounds per minute • Max Range — 1300 m (PG-15V), 4500 m (OG-15V) • Velocity — 400 m/s at the muzzle, 665 m/s maximum (PG-15V); 290 m/s at the muzzle (OG-15V) • Sights — 1PN22M, 1PN22M2 • Wars — See list of conflicts

During the early 1960s, the Soviet Armed Forces issued a requirement for a new infantry transporter that was highly mobile, sufficiently armed to destroy comparable Western vehicles such as the M59 and the Schützenpanzer Lang HS.30, and allowed embarked infantrymen to fight from within its crew compartment. This concept evolved into the BMP-1. The BMP was initially to be armed with a 23mm autocannon, a choice directly inspired by the success of the West German HS.30. However, the Soviet government had invested heavily in the development of anti-tank guided missile (ATGM) systems and discussion soon shifted to arming the BMP with missiles. This would allow it to defend itself against main battle tanks. The KB Priborostroyeniye design bureau in Tula soon proposed a specialized turret carrying both a low-velocity smoothbore gun and a mount for 9M14 Malyutka ATGMs. The purpose of the gun was to destroy tanks at closer ranges where the missiles were largely ineffective.

• Illustration — Drawing of PG-9 HEAT projectile The 2A28 'Grom' smoothbore gun fires the same projectiles as the SPG-9 infantry light recoilless gun, but with a smaller propellant charge. Before 1974, the ammunition only consisted of high explosive anti-tank (HEAT) rounds; the PG-15V HEAT fixed fin-stabilized rocket-assisted round. After 1974, OG-15V HE-Fragmentation projectiles were introduced. In the Ob'yekt 765Sp3, the standard ammunition load is 24 PG-15V HEAT rounds and 16 OG-15V HE-Frag rounds. The PG-15V HEAT round weighs 3.47 kg and uses a 2.6 kg PG-9 shell with a 0.322 kg RDX explosive charge in the warhead. A small PG-15P powder charge is used to boost the projectile from the gun barrel at 400 m/s. Once the projectile has travelled 10 –, the rocket motor starts and accelerates it to 700 m/s. The OG-15V HE-Frag round weighs 4.57 kg, it uses an OG-9 shell with a 0.73 kg TNT bursting charge. The muzzle velocity of the OG-9 is 290 m/s. The OG-15V is loaded by hand as it is too short to be handled by the autoloader. 2A28 Grom turret has a launcher for Malyutka and Malyutka-M ATGMs.

The HEAT warhead can penetrate 280 – of steel armor—more than enough to penetrate the frontal armor of NATO main battle tanks (MBT)s of the 1970s, such as the US M60A1, the British Chieftain or the German Leopard 1. The modernised PG-9 shell is able to penetrate up to 400 mm of steel armor. On the ranges, the PG-9 proved capable of hitting a 2 m high target at a range of 765 m, while its maximum direct fire range is 1300 m, reduced to 400 m at night, due to the limitations of the night vision system. Under battlefield conditions, it has a maximum effective range of 500 m. Maximum effective indirect range of the OG-15V HE-Frag round against formation targets is 4400 m. Its effective direct fire range against small point targets is around 1000 m. • Illustration — Close-up of a Czech BPzV-1's turret, 2 July 2005. Note the ATGM launcher for the 9M14M Malyutka-M A coaxial 7.62 mm PKT machine gun is mounted to the right of the main armament for which the BMP-1 carries 2,000 rounds in belts of 250. They are stowed in two boxes under the main gun. The machine gun has a rate of fire of around 800 rounds a minute. The 2A28 "Grom" gun and PKT coaxial machine gun cannot be accurately fired while the vehicle is moving over rough ground. This means that the BMP-1's main armament is less capable than modern stabilised autocannons, which can be fired accurately while moving. The BMP-1 is unable to engage targets using the 2A28 "Grom" gun from some hull-down positions due to its limited depression, making it vulnerable to enemy fire. The limited elevation of the main gun, its lack of firepower and inaccuracy against point targets at 500 - meant that it could not fight effectively in the mountains of Afghanistan.

• Illustration — Namibian Wer’wolf MKII MRAPs armed with the 2A28 Grom. In Soviet and Russian service, the only other armored fighting vehicle besides the BMP-1 known to have utilized the 2A28 Grom was the BMD-1. However, it is also mounted on other BMP-1 inspired designs, like the Chinese Type 86 (WZ-501) and the Iranian Boragh. Both the Armed Forces of the Islamic Republic of Iran and the Cuban Revolutionary Armed Forces are known to possess a number of wheeled BTR-60PB armored personnel carriers retrofitted with the complete turret and main gun assembly of the BMP-1. There is a fire support variant of the WZ-551 in Chinese service equipped with the 2A28 Grom in a modified turret. The Namibian Army currently operates a variant of the WZ-523 and the Wer'wolf MKII APC mounting the BMP-1 turret. In May 2024, in the context of the 2022 Russian invasion of Ukraine, the Russian military was seen using a towed version of the system, seemingly cannibalized from armored vehicles. Later same year in July 2024, another video appeared online showing crudely assembled 2A28 Grom gun, still attached to BMP-1 turret ring, with civilian trailer and tractor for transportation. The video shows members of the 25th Combined Arms Army transporting the artillery piece into position, uncoupling the gun from tractor and stabilizing it on metal supports fitted on rails welded to the turret ring. This allows the gun assembly mounted inside the ring to move horizontally. The gun lays on it's supports while firing, as ordinary commercial trailer can't provide enough resistance to recoil of the gun.