I think that Osage Orange (or Hedge, as it's known in Kansas) would look great on a blue gun if you find a piece with a good grain. I agree with others that after it dries it becomes very hard. Hedge is still popular for fence posts because it weathers so well and is incredibly resistant to rot.

One positive using Osage Orange for grips, if you lose your revolver outdoors, the grips will still be there after the steel rusts away!