It's probably worthwhile to distinguish between "dirty" and "incompletely burned".  All the IMR rifle powders are pretty much the same composition and, if burned completely, leave the same (minimal) residue. Your 4350 load may look "dirty" when what's really left behind is unburnt powder.

If QuickLOAD estimates are believed, 4350 gives only about a 92% burn with that load, while 4895 would give 100% to reach the same velocity at safe pressure.

(Edit: "Predicted data" removed to preclude mistaking for "tested data")