Dirty powder

[ninepointer]

The afore-mentioned POWDERS are relatively clean-burning . Have you ever tried UNIQUE ? --- Especially the older version , the newer type burns cleaner . --- I use it behind cast-bullets (handgun and rifle) . --- It's a good powder (for light loads) but leaves the bore looking like a smokestack .

Not sure if this applies to rifle cartridges (I only reload shot shells) but cold temperatures will also make for dirtier burning, especially in low-pressure loads.