Barrel has not been cleaned since before last turkey season 2010.  Temperature was 57 degrees. Windy.  42 yards from end of barrel to target.
Please note, my forcing cone has been lengthened, and barrel ported. Barrel is 26 inches.
20" pattern is approximate, as I only measured from center to North, South, East, and West outer edges.
JH .655  295 in 10" circle  224 in 20" circle

Rhino .660   326 in 10" circle   195 in 20" circle

God Bless,
David B.