I doubt if it would work worth spit to be honest with ya. But I've not tried it either. You would need to find a tight barreled .50 and that would be luck of the draw with most brands. My guess is that XTP mag has a pretty good jacket and it wouldn't expand well at all. Bullets I've looked at and thought might work in the manner you describe are the Rainier lead-safe line. The copper on those is mostly a pretty thin coating best I can tell.