231 is "dirty" .... nonsense.
Perhaps compared to a virgin, NIB, unused gun, but it is one of the cleanest powders out there.
Now, the powder fouling does tend to mix with certain bullet lubes and create a gooey sticky grey/black mess. So trying different lubes might help a lot.
A good crimp helps too. 231 likes a nice firm crimp with good neck tension. Doesn't have to be really tight like the big loads, but not loose.
None of which is a problem if you clean your gun.
I shoot a lot of 250-255gr bullets over 7.1grs of 231. Nice factory level load.
Joe