I can't answer your question as to how far out these are lethal but for me, the round is lethal further than I'm comfortable taking a clean shot. I've used the 168 VLD in my 7mm WSM to take both Elk and Whitetail. Closest shot has been inside 40 yards with the longest shot inside 400 yards. Every shot has been a through and through with massive internal damage. If they didn't drop in their tracks, they didn't go far. The lethality of this round at practical hunting ranges is unquestionable.
Early on, folks had me worried this round may be too "fragile" for Elk but, that hasn't been an issue for me. I also have some 300 grain Bergers for the 338 Mag that may get called into service next season but I have the opposite worry there with those possibly not expanding as much as I'd like...