I have a cz75b 9mm and a Cz75b .40. The barrels do not appear to be the same OD when placed end to end. I also do no intend to do any of the smithing work myself...that's why I have contacted the custom shop. I don't care how they do it, I'm looking for a drop in product.. Happy with that? Since I want to use the .40 chassis, I assumed it would be best to use the .40 bbl contour. Copy?