The adjustable charge bar, hereafter referred to as the ACB, takes on a very irregular shape, when set for very low charge volumes. When using more coarse powders, the disks do better with their round apertures, although you may have to compromise in the charge weight achieved by maybe a tenth of a grain. I just switched from ACB to disk using a small cowboy load of Trailboss with its relatively big, disk-shaped flakes. I was getting rounds with very low charges, I presume because the ACB was clogged. The ACB opening looked like the shape of my mouth, set for 3.0 grains. With the disk, I had to settle for 3.1, well within the cowboy velocity rating range.