I have used jacketed ammo to clean out lightly leaded barrels. Works great. A cylinder full cleans out leading nice. I would not do this on a heavy leaded barrel, as pressures will rise. As suggested in an earlier post, a Lewis lead remover works great. They are marketed now under various names. I would not use steel wool on your barrel. Cylinder yes, barrel no. Although it works great, it will eventually score your barrel, affecting accuracy. Get bronze wool, sometimes marketed as Chore Boy. Available online or your local grocery store. This has all the advantages of steel wool, without damaging your barrel, as it is softer than steel. Just wrap some around an old cleaning brush, making a snug fit in your barrel, and you are good to go.