It can be done without worries so long as it's done properly. I've had my .41 mg BH drilled & tapped with optics for years. Some will go off on the "value" thing and well, yeah it may detract from it's value but then again, it's a common variant New Model so there's no collector value there anyways. I always figured if I'm worried about collector value, just don't shoot the darn thing to begin with.
