I finally got an answer from Remington on the turkey choke tube supplied with the gun. The inside constriction is .060 and the inside diameter is .675 . I checked Carlson's Remington Pro Bore choke tube and it's inside diameter is .665 (thank the Lord it isn't one-thousandth more, lol). I'll have some pattern work to do, but my guess from these numbers are the Remington .675 will probably do good to 30 yards, & the Carlson's tighter choke of .665 might get me out to 50 yds. with the Hevi-13's. If anyone has patterned their Versa Max please let me know what you found out. Thanks