Go to the grocery store, and pick up a "Chore-Boy" pad. It is made of copper, if I remember right, and designed to clean pots and pans, and will not harm a gun barrel, unlike long term use of harder steel wool can. Wrap some on a slightly worn brush, add a little solvent, and run it thru the barrel a couple times. You will be amazed at the amount of lead it removes. Works well on handguns and rifles as well. Basically its a poor mans version of the Lewis Lead Remover.
Larry