bolt air passages design
 

I need your help on how to design the most most efficient CO2/compressed air passages of the bolt of a paintball gun. It should be the highest flowing design knowing the fluid released vertically from a valve has to come out of the barrel horizontally. Stock bolt passages have the input bore radial to the the output bore. Some aftermarket bolt have a ramped inlet which is higher flowing. Also there is a restriction at the output of the valve (1/4" diameter hole).

Which free software would suit to help me find the highest flowing passages (input bore angle and passages diameters) ? Could you give some advises (I can provide more info) ?