Please explain the dimension reference of 0.021 inches. My company manufactures very specialised HE and AP rounds for military use. The round that we have designed has a diameter of 17.80 mm (.700 inches). We have no problem with the M4 Super 90 that sports a modified interchangebale choke as this has a min internal diameter of 17.88mm (.703 inches) BUT the fixed choke appears to be a lot smaller than typical modified choke dimensions. Is this correct?
Did the US Marines only buy the model with a fixed choke? What type of choke is used in the fixed choke model? What is the minimum diameter of the fixed choke? I have a limited edition M4 Super 90. Why does the fixed choke on this model not have the same minimum internal diameter as any of the Benelli interchangeable chokes?