TsKIB-SOO A91-B in 5'56x45mm-NATO
The TsKIB-SOO institute, a subsidiary of KPB Industries of Russia, produces this bull-pup assault rifle since the second half of the 1990s. The first ever version of the A91 was trialed as a contender for the replacement of the KALASHNIKOV AK-74 and AK-47 rifles as the main long arms of the Russian Armed Forces. The trial was ultimately won by the "Abakan" rifle, a.k.a. the IZHMECH AN-94 "NIKONOV". TsKIB-SOO has later upgraded the design and offers it for export on the Military-LE market; the weapon as you see it in this pic was shown at the IDEX 2003 expo. Although another version of this weapon was already available since two years (externally similar, but chambered for the .7'62x39mm-Soviet round), this new design fires the .5'56x45mm-NATO, feeding from proprietary 30-rounder magazines. It has an underbarrel-integrated grenade launcher that will chamber the proprietary, self-propelled VOG-25 grenade, currently used only in Russia. The A-91 series of Bull-Pup weapons was the FIRST ONE EVER to adopt a frontal spent cases ejection, such as the one used in the .5'56x45mm FN F2000 belgian modular Bull-Pup assault rifle. The A91-B in the .5'56x45mm-NATO has a total lenght of 670 Millimeters, and an unloaded weight of 3,4 Kilograms. Mechanically, it is an interesting upgrade of the AK action. It still hasn't found adoption in any way, though.
Photo and information from: PIERANGELO TENDAS