The powder in the mid section is caused by static electricity, causing powder to migrate up the hull. Rub a hull with your fingers, and then drop a load of powder. Depending on what powder you use, you will notice many flakes sticking to the inside walls, well up the hull. No wad will 'scrape' all of the flakes off of the wall.
When it's dry, handle hulls the least amount you can.
When it's dry, handle hulls the least amount you can.
