Reply To: Seeking air stripper info
When I built my air stripper (no shroud), I chose the gap to be the bore diameter long. The diameter of the stripper for a caliber .177″ is .225″. The cone is 45 degrees included angle and creates a sharp edge. I have six vents (5/32″ x 1/2″) that give a total gap area of .469 square inches.
This is by no means the only approach. Many are right angles to the bore with round vent holes.