[Unclenick]

Dirty cases and erratic ejection both suggest low pressure. HS-6 and other slower spherical propellants function better as pressure increases. They are not very efficient for minimum loads, and a chronograph typically shows a lot of velocity variation at lower pressure, indicating inconsistent ignition. They do much better as you move toward maximum pressure.

For good function with lighter loads, use something a little faster. Power Pistol may do well for you if you are looking at full powder loads, but for more versatility and a wider load range (from target to standard ball load power) try Hodgdon Universal.