There were some SKB 12ga sxs made for the American market with factory IC/M chokes and 28" barrels, but they're pretty rare. The first sxs I ever bought (Rota, Spain--US Navy Rod & Gun Club, 1972) is a Model 150 set up that way. However, I have never seen a 20ga with 28" barrels choked anything but M/F. And agree with Chief that I've never seen a 26" 12 (or a 25" 20--why did they make the short 20's an inch shorter?) choked M/F.