2A28 Grom The 2A28 Grom is the main armament of the BMP - 1 Infantry fighting vehicle . Description . The 2A28 is a 73 mm low pressure smoothbore semi - automatic gun with wedge breechblock . The gun is relatively compact and weighs . It is fed from a forty round mechanized conveyor double - row magazine located around the turret ring of the BMP . In the BMP , the gun is brought to bear by electric motor , with a manual mechanical backup . The maximum horizontal and vertical traverse speed with the electrical system is 20 ° / s and 6 ° / s respectively . Minimum horizontal and vertical direction rate is correspondingly 0 . 1 ° / s and 0 . 07 ° / s . The gun can be depressed and elevated between – 4° and + 33° , with aimed fire possible up to an elevation of + 15° . The turret can traverse 360° . Cyclic rate of fire is between 8 and 10 rounds per minute , with the gun returning to an elevation of + 3° 30 ' to reload after each shot if the autoloader is used . The gun is reloaded by the M3 electromechanical autoloader with ammunition conveyor , but can be reloaded by hand if necessary . The autoloader is not reliable ; it can break down from vibration when the vehicle is moving at high speed over rough ground , and its operation is a danger to the gunner ' s fingers . Using the autoloader , the gun has a rate of fire of 6 – 8 rounds per minute while a skilled gunner could easily achieve 10 rounds per minute . These drawbacks caused the autoloader to be removed in Ob ' yekt 765Sp3 and Finnish BMP - 1s . Some units removed the autoloader altogether when new vehicles were delivered , but the mechanized ammunition conveyor magazine was kept . Ammunition . 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 consisted of high explosive anti - tank ( HEAT ) rounds only ; the PG - 15V HEAT fixed fin - stabilized rocket - assisted round . After 1974 , OG - 15V HE - Frag mentation 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 and uses a PG - 9 shell with a RDX explosive charge in the warhead . A small PG - 15P powder charge is used to boost the projectile from the gun barrel at . Once the projectile has travelled , the rocket motor starts and accelerates it to . If this low speed projectile ' s fins catch a crosswind it tends to " shuttlecock " with a consequent reduction in accuracy . The OG - 15V HE - Frag round weighs , it uses an OG - 9 shell with a TNT bursting charge . The muzzle velocity of the OG - 9 is . The OG - 15V is loaded by hand as it is too short to be handled by the autoloader . Performance . The HEAT warhead can penetrate 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 of steel armor . The BMP - 1 ' s gun is unable to penetrate the front armor of modern NATO MBTs such as the US M1A1 Abrams , the British Challenger 2 or the German Leopard 2 but it has been claimed that it can penetrate the side armor of these tanks in some areas . On the ranges the PG - 9 proved capable of hitting a high target at a range of , while its maximum direct fire range is , reduced to at night , due to the limitations of the night vision system . Under battlefield conditions it has a maximum effective range of . Maximum effective indirect range of the OG - 15V HE - Frag round against formation targets is . Its effective direct fire range against small point targets is around . 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 200 - 250 rounds a minute . The 2A28 ' Grom ' gun and PKT coaxial machine gun cannot be accurately fired while the vehicle moving over rough ground . This means that the BMP - 1s main armament less capable than modern stabilised autocannons which can be fired accurately while moving . The BMP - 1 is unable to engage tanks and APCs using the 2A28 ' Grom ' gun from 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 meant that it could not fight effectively in the mountains of Afghanistan . The BMP - 1 was a threat to NATO APCs , light AFVs and even MBTs , from the PG - 15V shell at short range , and the 9M14M " Malyutka - M " anti - tank guided missile ( ATGM ) at longer ranges .