Russian Air .50 Cal!
The YakB is a .50 caliber (12.7mm x 108, not the 12.7mm x 99 like our .50 BMG), 4 barrelled, gas operated(!), Gatling type gun used on the Mi-24 Hind D attack helicopter-troop transport. I found this while rumaging around in a scrap metal dump outside Kirkush Military Training Base (KMTB), in sight of the Iranian Zagros mountains (on a clear day). (And yes, that's a KNJ shoulder holster, the best one I've found for quality, durability, and economy. It was one of the first items my replacement bought from me!!)