Shotgun Cleaning?

I was talking to a fellow about a problem cleaning my barrell. I have to shoot slugs for Deer in the county that I live in. I can clean that barrell all day and the patches keep coming out Black.
I was told it is plastic fouling from the wads from the slugs I've been using. Does anyone have any ideas or solution to to this problem? The gun shoots slugs
very accurately. It drives me nuts!

There are cleaning solutions at the gun store that dissolve or loosens the plastic from the jackets. You have to look at the labels. A good plastic or brass brush is needed too!

You can use just about any solvent, and it will help remove the plastic, but the best item I have found for shotgun cleaning, whether it be lead from foster type slugs or plastic fouling (my steel shot wads leave a lot of plastic in the barrels) is a brush called the "Tornado" brush.....I can't remember for sure if it is made by Outers or Hoppes, but I believe it is one of those two companies.
The 'brush' looks like a bunch of wire loops connected to a central spindle. I simply run a heavily soaked patch through the bore and let it soak overnight, then the next day dip the brush in the solvent and run it through....If you do have heavy plastic fouling, it will come out looking like black snot! (Yuck!). I usually do a dozen or two strokes through the bore, run some tight cloth patches through, then repeat the process. Any lead buildup from the slugs will come out as silver flakes.
Good luck....................