Volume vs Pressure

Okay I have been researching PCPs for the last year trying to decide what I should buy and what the best setup is. I pulled the trigger and have had a Condor SS 25 for 3 weeks now, and would really like to regulate it for more shots and lower spread on fps. I really want power and shot count and everyone says it’s impossible, but my mind says different so off to thermo and fluid dynamics to figure it out.

I had a targeted velocity with a specific weight and worked toward the best efficiency of that energy. I began attempting to figure out the best regulated pressure, and what I found out was surprising.

The regulator acts as both an orifice and flow regulator, so I needed to figure out a chamber between the regulator and valve to maintain a constant pressure to the barrel. I found the open regulator to crippling the efficiency and power, in other words a bottle to provide one shot is the most efficient unless the regulator does not restrict flow. The calculations I ran showed that for each barrel length, specific projectile, and velocity the single shot tank volume and valve open time changed.

Here are the thoughts I have observed from calculations.

1. At the perfect pressure for the particular barrel, projectile, and velocity the single shot chamber should be as large as possible. In other words the pressure drop from the time the valve opens to the time the valve closes should be 0. The tank size is not as critical for lighter pellets.
For example:
25 cal 32gr at 900fps with a 490cc tank @ 1600psi will push the pellet to 900fps and can be refilled with a 490cc tank @ 3000 psi 72 times. With a 17cc tank @ 1600psi (900fps) can be refilled with a 490cc tank @ 3000 psi 67 times.
25 cal 50gr at 900fps with a 490cc tank @ 2200psi will push the pellet to 900fps and can be refilled with a 490cc tank @ 3000 psi 23 times. With a 17cc tank @ 2200psi (900fps) can be refilled with a 490cc tank @ 3000 psi 19 times.

2. A bigger tank does not necessarily mean higher quantity of shots or higher velocity, it may only add 2 to 3 more shots than a smaller tank.

Theories and calculations cannot replicate actual testing. These calculations will help me get in the neighborhood of what I want, before I spend hours trying to achieve it. So when I get the money together and find a fabricator my intentions is to build a small tank 4ci (65cc) and fit it with my high flow spin-lock tank valve. Mount bellow the small tank my AF 490cc tank. The 490cc tank will have a regulator then be plumbed into an on/off valve and then to the fill side of the original AF valve. According to my calculations this should give me around 70 shots of a 32gr JSB at 900fps.

Now I need to figure out how to get my valve to stay open the perfect amount of time.