The Azerbaijani government are now manufacturing a .50 BMG version of their monster semi-automatic 14.5mm IST-14.5 “Istiglal” rifle. The IST-12.7 was on display for the first time at the Africa Aerospace & Defense expo 2010.
The IST-12.7 magazine holds seven rounds, two more than its big brother. The 43″ barrel is not detachable for transport, unlike the IST-14.5. It has a slightly different stock, kind of resembling an M4 stock, and a receiver length rail for optics. I think these two changes have been added to make the gun more appealing to the export market.
[ Many thanks to Peter and Rolf for the information. ]