"That's because the bullet is a composite metal. It's not solid steel, and lead was too soft to hold up for the range. And Cable and Rattler wanted something with more impact power than just steel, so it's got adamantium in it. It's incredibly dense, hence the weight. And that's a special mix of gunpowder in there too for the distance. I think the max range before accuracy was lost was at a mile and three quarters, but I dunno if anyone's mutant powers were factored into that little trivia tidbit or not, so I wouldn't personally peg it at more than a mile, mile quarter tops."