mcawful, the 20gr by vol. should do it. You might also try felt wad I have had very good luck with them in good barrels. I use the felt stripping they use for weather seal from the hardware store and cut my own with a 1/2 indh wood plug cutter also from a hardware store. You can also get different size cutters from some of the shot gun supply places like Dixie gun worksor the Possables Shop if you wish to buy them. The felt wads work best for me if they are a bit oversized and greased with bore butter.Lee
http://www.possibleshop.com/wads.htm
http://dixiegunworks.com/
http://www.octobercountry.com/products2.php?categoryid=380
http://www.three-peaks.net/muzzle.htm