The MARCK-15 AR Hydra Platform in 9mm packaged with 5.56 NATO, 7.62×39 and .300 Blackout conversions all in one rifle case OLD TOWN, ME (June 2014) – MG Industries, manufacturers of the MARCK 15 “Hydra” platform, announce the creation of several “packages” of their famous, highly-configurable, modular AR-15 style rifle with certain calibers to create...