I have both Blackhawks and Bisley's and both bash my knuckles.
The fix is grips with a filler behind the trigger guard. Pachmayr or Hogues for the BlackHawk, and grips I made or Eagle grips for the Bisley as no one makes rubber that I am aware of.
The Eagle grips do require fitting as Bisley frames don't seem to be consistant in size and shape.Pictures on bragging board of my Bisley with Eagle grips and my own version instaled.They take the bite out really well and are LOTTTTTT'S easier on big hands.