The 73 mm 2A28 is a smoothbore, low-pressure rifled gun with a short recoil that has been specially designed to suit the requirements of mountings on light armoured vehicles. It fires a special fin-stabilised HEAT round, which is also used by the infantry SPG-9 antitank weapon. When fired, the projectile has an initial muzzle velocity of about 400 m/s which rises after a period to 665 m/s; this means the projectile may be prone to the influences of high side winds. The usual installations feature an automatic loader which loads the gun when it is elevated to +3°30', limiting the rate of fire to around 8 rds/min. The gun barrel has provision for the installation of a 'Sagger' wire-guided ATGW above its junction with the turret mantlet.
It is understood that some countries have removed the automatic loader from the BMP-1 as this is unreliable in service.
Ammunition for the 73 mm 2A28 gun is available for a number of sources. The Bulgarian Vazovski Machinostroitelni Zavodi, for example, manufactures the following types: OG-15V(HE), OG-15VM(HM), PG-15V (HEAT) and the PG-9N (HEAT). The first two of these have a muzzle velocity of 290 m/s and a maximum range of 4.5 km while the latter two have a muzzle velocity of 400 m/s and a maximum effective range of 1,300 m.
Production as required. Installed on the BMP-1 ICV and the BMD-1 airborne combat vehicle.