Time for the reveal of a few secrets. How to quickly find out how minor changes may effect your energy output in a traditional pcp. For these simple solutions, you need to know some of your rifles specs.
***Port size Increase/Decrease***
Port OD / Bore OD
.2 / .25 = .8
What is your energy output 80% of? Lets say this rifle is at 60 fpe.
60 fpe is 80% of 75. (60/80 = .75)
New port size = .225
.225/25 = .9
Your new energy output with this port size should therefore be 75*.9 = 67.5 FPE. To obtain this you will need your projectile to be roughly 1/2 grain per fpe, ie: 67.5/2 = 33.75 gr. No considerable changes in hammer strike should be needed. Increased air consumption to be expected.
***Plenum Increase/Decrease***
Plenum volume = 30 cc
Increasing volume to 50cc
CC use per shot = 5
Setpoint = 2000
2000*30/35 = 1714 psi
2000*50/55 = 1818 psi
1818 - 1714 = 104
104 / 2000 = 5%
30 cc energy output = 60 fpe
50 cc energy output = 60 fpe * 1.05 = 63 FPE
To obtain this you will need your projectile to be roughly 1/2 grain per fpe, ie: 63/2 = 31.5gr. Slight increase in hammer strike will be needed. Increased air consumption to be expected.
***Pressure increase/decrease***
Regulator pressure / Set point = 2000
Increasing to 2200
2200/2000 = 1.1
Energy output at 2k = 60 fpe
Energy output at 2.2k is therefore 60*1.1 = 66 fpe
To obtain this you will need your projectile to be roughly 1/2 grain per fpe, ie: 66/2 = 33gr. Additional hammer strike will be needed to overcome the additional pressure holding the valve closed. Increased air consumption to be expected.
***Barrel Length increase/decrease***
Old Barrel length 20"
New barrel length 22"
Energy output at 20" = 60 fpe
60 / 20 = 3
3 * 22 = 66
New energy output potential = 66 fpe
To obtain this you will need your projectile to be roughly 1/2 grain per fpe, ie: 66/2 = 33gr. Additionally you will be required to create more dwell/lift and use more air to make use of the additional barrel volume.
And there you have it, some backwards, napkin math, for known pcp configurations and what energy you can expect when modifying the above parameters. Simple ain't it? These are all ballpark approximations, and the barrel calculation is by far the most unforgiving due to its dynamics, but will get ya within reason.
***Port size Increase/Decrease***
Port OD / Bore OD
.2 / .25 = .8
What is your energy output 80% of? Lets say this rifle is at 60 fpe.
60 fpe is 80% of 75. (60/80 = .75)
New port size = .225
.225/25 = .9
Your new energy output with this port size should therefore be 75*.9 = 67.5 FPE. To obtain this you will need your projectile to be roughly 1/2 grain per fpe, ie: 67.5/2 = 33.75 gr. No considerable changes in hammer strike should be needed. Increased air consumption to be expected.
***Plenum Increase/Decrease***
Plenum volume = 30 cc
Increasing volume to 50cc
CC use per shot = 5
Setpoint = 2000
2000*30/35 = 1714 psi
2000*50/55 = 1818 psi
1818 - 1714 = 104
104 / 2000 = 5%
30 cc energy output = 60 fpe
50 cc energy output = 60 fpe * 1.05 = 63 FPE
To obtain this you will need your projectile to be roughly 1/2 grain per fpe, ie: 63/2 = 31.5gr. Slight increase in hammer strike will be needed. Increased air consumption to be expected.
***Pressure increase/decrease***
Regulator pressure / Set point = 2000
Increasing to 2200
2200/2000 = 1.1
Energy output at 2k = 60 fpe
Energy output at 2.2k is therefore 60*1.1 = 66 fpe
To obtain this you will need your projectile to be roughly 1/2 grain per fpe, ie: 66/2 = 33gr. Additional hammer strike will be needed to overcome the additional pressure holding the valve closed. Increased air consumption to be expected.
***Barrel Length increase/decrease***
Old Barrel length 20"
New barrel length 22"
Energy output at 20" = 60 fpe
60 / 20 = 3
3 * 22 = 66
New energy output potential = 66 fpe
To obtain this you will need your projectile to be roughly 1/2 grain per fpe, ie: 66/2 = 33gr. Additionally you will be required to create more dwell/lift and use more air to make use of the additional barrel volume.
And there you have it, some backwards, napkin math, for known pcp configurations and what energy you can expect when modifying the above parameters. Simple ain't it? These are all ballpark approximations, and the barrel calculation is by far the most unforgiving due to its dynamics, but will get ya within reason.