Heckler&Koch and maybe soon to be known as Poors&YEET in light of the news the H&K is in dire financial straights has announced they are making their MR556A1 upper receiver available for civilian purchase directly through their website.
-Complete MR556 Upper Receiver/Barrel Assembly— HK 16.5 inch cold-hammer forged barrel, upper receiver with forward assist, extended convertible charging handle, HK -Free Floating Rail System handguard
-Complete MR556 Bolt Group Assembly
-Tungsten Filled HK Proprietary Buffer
-HK Proprietary Buffer (Action) Spring