To really get lead, copper, and plastic fowling out you need a quality commercial solvent. People have used kerosene and claimed it worked, but personally I never tried it. I've used Birchwood Casey Bore Scrubber and Birchwood Casey Products ever since poster Triple Se7en recommended them to me. I have been so pleased with the cleaning and protection I get from them, that while I do experiment with other things, I trust Birchwood Casey.

After the bore is good and clean put some quality gun oil like Birchwood Casey Sheath, Rem Oil, Kroil Oil, Breakfree, or any good gun oil and swab the bore of the rifle to protect it against rust. Before you shoot it next, take a patch and put some isoproply alcohol on it and swab the bore good. Then run two dry patches through the bore. Now the oil is removed. With the drypatch still on the jag/ramrod at the bottom of the breech, pop a 209 primer through the rifle. This will clear the breech plug of any fowling. Pull the patch and check to make sure there is a good burn mark on the patch. This indicates the fire channel is clean. Pop another 209 primer through the rifle to fowl the breech plug. I do this, some do not. All a matter of choice. Now load as normal and have fun on the range again.