Get a jug of Gunzilla , soak the bore over night wetting it with a cloth patch and the next day push a tight patch on a jag through the bore. It will lift lead out of a bore better than anything I have used in the last 50 years. A tight patch will squeal like a little pig as the cloth snags the Gunzilla de-solved lead and carbon deposits.
It is a water-less, and petroleum-less plant base bore solvent that dissolves lead and carbon. I still use water to dissolve BP fouling but then follow up with Gunzilla to take out the lead and carbon fouling. It also leaves a protective coating to prevent corrosion. Nothing, not even Gunzilla dissolves the BP fouling as fast as plain ole tap water and a bit of dish soap but soap and water won't touch lead or hard carbon fouling.
I get Gunzilla at my local gun shop which is about to close after 53 years of continual operation, sad day indeed! I'm sure you can Google a source of Gunzilla on line.
Most of my shooting club uses Gunzilla and they all shoot cast bullets in gong competition exclusively.
