i agree that on a cocker closed bolt is an advantage because it was designed that way. YOu can make an open bolt cocker pretty easily but you will see negitive effects. On mags for example open bolt works best and closed has disagvantages(like not being able to operate).
In truth all markers fire in a closed bolt position.
-Minimag Body HR
-Z grip with extender
-12V X-Boarded Revvy
-6 barrels including:10 Inch DYE SS, 8 inch Steel Wind, 8 inch stock minimag barrel, 12 inch BOA barrel, 12 inch Lapco Autospirit, 16 inch SPAA