It's likely that the cartridge is too long (and the base too large) for disassembly with most commercial inertia pullers. You'll probably need to use a collet type puller. Don't expect the powder charge to come out easily. The old black powder is probably a solid mass.

I assume you have a reloading press and the proper shell holder. Consider drilling a hole in the nose of the bullet and screwing in a screw. Put the round in the shell holder and run it up in the press. Clamp a vice grip on the screw and lower the ram. The bullet will be easily removed and none of the surfaces you intend to measure will be harmed.