|Place of origin||Soviet Union|
|Designer||B. M. Zorin
P. N. Korolev
Work on the caseless rounds began in interbranch competition announced by the Ministry of Defence Industry of the USSR in 1972. The experimental series of weapons using the 5.6-mm caseless cartridge designed for Izmash (now Kalashnikov Concern), received the name of AB. A feature of this scheme is the lack of a cartridge case. The bullet is inside the compacted propellant block, which is almost completely consumed in combustion, and therefore there is no need for an extraction/ejection mechanism. However, studies revealed unsatisfactory reliability of storage of the caseless cartridge, uneven burning of propellant at low and high temperatures (powder crumbles or breaks into pieces), which led to instability of the pressure in the bore. There were also problems with the obturation of the projectile, which in the standard cartridge configuration is provided by the cartridge case.