The Hungarian Gepard family of rifles has a bumpy history. The first models were difficult to reload and the soviet 12.7 x 108 mm round had significant and uncomfortable recoil. Future models mitigated these problems by eventually introducing semi-automatic actions and a recoil system that featured a reciprocating barrel. The 12.7x108mm round is similar to the revered .50 BMG, but has a longer case and 20% more powder, resulting in slightly higher muzzle velocity and comparatively extended range.
This is the GM6, the last iteration of the Gepard series of rifles. It is, in a word, nuts. It’s a recoil operated, semiautomatic bullpup antimaterial rifle with a five round magazine that can be fired from the hip. As if that wasn’t enough, the designer evidently believed the 12.7x108mm round, while still among the most powerful in the world, was inadequate. So the GM6 is chambered for 14.5x114mm, the same round used in the ZPU antiaircraft guns. The ballistics on this round are, also, nuts, delivering a .57 caliber armor piercing and incendiary bullet at a muzzle velocity of 1000 m/s resulting in 32,000 Joules of energy delivered on target.
How bad ass is all that? Check out this video and see for yourself.