Heres a very rare, and completely functioning, handheld minigun chambered in 7.62x51mm.
This guy puts it through the wringer to see just how effective his AR500 armor is and whether this gun can pierce through it or not. The recoil proves a bit too much to handle though! Check this out as he goes fullmag and theres some great slow motion footage revealing the impact on the armor.
Read more: http://damn.com/ultra-rare-handheld-minigun/