Am I reading correct that the CRIO chokes do not match the M4? I'd like to use an M4 as a turkey gun and would really like to try the extended turkey choke, but the charts on the Benellis site don't show as a match but the M2 does. To me this does not make much sense as you'd think that they would have a standardized thread and backbore dimension.

Nobody has a "standardized thread and backbore dimension" across their entire line over the years.

Well I'll answer my own question here. The Benelli M4 uses a Mobil style choke and from what I have learned most any modern/mainstream Benelli choke tube will work including the extended CRIO chokes. The ex-long CRIO chokes are apparently just going to look goofy.

George Trulock of Trulock chokes was a big help and provided me with the part number of his choke that best suited my request.

I don't know about that information. Are you saying Mobile Chokes and Crio Chokes are interchangeable? That doesn't seem right.

From my personal experiance yes it is correct to a degree. However from what I have seen is that the crio's are a slight bit longer. Some crio chokes will not tighten down before bottoming out.