Oh No! From your pre-oven-cleaner pic, getting a closer color match would have been pretty easy. I would have suggested mineral spirits clear the BLOicon you applied, then dilute some Birchwood Casey walnut stain with water, and rub the forend to even out the color. Let it dry. If too light in color, do it again. If too dark, go over with plain water. When it matches to your liking, use the BLOicon. I have matched a few handgaurds like this.