Got around to weighing the .450 Marlin.
It's 9 lbs without the sling. That's more than the Marlin 1895 45-70 lever action by a good bit, especially if you're the one packing it through rough country. On the other hand, I'm shooting significantly hotter ammo that the lever gun will handle (READ: More Recoil), so the extra weight isn't a bad thing.
Since I'm going to be 75 years old in February and have no intention of humping this sucker more than a few miles at most, I'm happy to live with it.