Carlson 575 throws a great hunting pattern out of every 20 gauge I have tried it in. All my guns have a Carlson 575 except 1 and it has the factory 585.
I just tried a Remington factory .572, Carlons Longbeard .568 and a Carlson's TSS .555. Loads tried were Win Double X, Longbeard XR, Remington Nitro and Federal TSS. Across the board, the .572 did best. I think the .555 was over-choking and my patterns were blowing open.