dirty as sin in my 45 Colt... less so in my 357... but for a plinking powder i cannot beat it... for "serious" 357 loads i go to WW 296, H110 and sometimes 4227...

WHen i was loading 40 S&W i would often use WW WST.. it was a low muzzle flash powder for night time used and it was often clean burning...

I also find that Hodgdon Longshot is pretty clean and can give some pretty good velocities and cleanliness... but only have played with it in the 45 Colt...