TsKIB SOO, a subsidiary of KBP (Instrument Design Bureau), have developed a new bullpup rifle called the ASh-12. It is chambered in a new family of 12.7x55mm cartridges they developed for the rifle.
The 12.7x55mm is a thumper of a cartridge. It is similar in size, and probably power, to the .50 Beowulf. To help mitigate recoil, the ASh-12 is fitted with a large two-baffle muzzle brake. The 12.7x55mm assault rifle cartridge is based on the 12.7x55mm subsonic rifle cartridge (similar to the .500 Whisper). I do not believe an assault rifle chambered in 12.7x55mm would be able to chamber the much longer 12.7x55mm suppressed rifle cartridge. TsKIB SOO have developed a FMJ, soft-point, lead and armour piercing loads for the 12.7x55mm assault rifle cartridge.
The ASh-12 is not the first bullpup from TsKIB SOO. In the mid-90s they developed the A91 assault rifle and in the early 00s, the A91M.
[ Many thanks to T.G. for emailing us the link. ]