Just got a Carlson's .575 choke tube for my 20 gauge 870. Tomorrow I will be testing lead 3" shells with the Remington Nitro Mag #4, Winchester Double X Magnum #5, Remington Nitro Turkey #5, and old Federal Premium Mag Shok #5. I will start all my shots on a 20"x20" target with a turkey head in the middle at 30 yards. I plan on shooting 3 shells of each ammunition.
Hopefully I get decent results by atleast 80 pellets in a 10" circle with one type of ammo.