Lyrurus tetrix and Tetrao urogallus: Birkhahn, Auerhahn
unfortunately practically extinct in central Europe, I do not know where it is still legal to hunt them.
Traditionally in Germany and Austria they where hunted in spring during rutting season, with shotgun or a rather slow bullet, never on long range.
6 mm Rem seems good for exploding the bird, not so good for eating it or displaying the trophy...

fuhrmann