There are way better powder measures out there, usually a few at the gun shows reasonably priced, or here on the classifieds. Gee, Ive probably got a couple of 'spares' buried in my shop like most of us long time reloaders, so just get a nicer one and save that one for what works best in it.
BTW, what residue you see in the barrel is not 'unburned' powder. If you doubt this, take a rod and dry patch and push it out onto a clean container and put it under a scope; or in a pile and try to light it off.