Austin
Do you know of any gunsmith that still usess that method for chokes. I have a sleaved 20ga hammergun that I need the chokes opened and do not trust someone to just open them up and hope the shot pattern is good.
David

What Austin says is correct of course but if you find a Parker 10 gauge with .040 of choke you can pretty well predict it wasn't made to an order for "improved cylinder" or "make for 40% pattern for decoy shooting". More likely, the special instruction was "make shoot close" i.e. full choke...