I was just playing around with the numbers and it appears (from your data) that .28's are actually the 'worst'. Now this is coming from a purely numbers standpoint and from someone who hasn't personally used .28's, take into account
Anyways here's what I came up with:
Kinetic Energy in Joules (excluding rotational energy obviously):
.20 - 2.005
.25 - 2.132
.28 - 2.084
.30 - 2.141
.36 - 2.177
.43 - 2.271
-These are the kinetic energies (KE) averages calculated from each FPS reading you supplied above.
-There is a clear trend that as the mass increases, the KE actually increases SLIGHTLY - with the only exception of .28's.
Think about this - your gun is able to transfer more KE into a BB's if there is more mass (neat!). Why? Well my theory is because the extra inertia (mass) will cause a higher pressure to be obtained behind the BB - as in it takes more time to move the BB so a slight increase backpressure is caused.
- Note that muzzle velocity is not the only factor in distance. Rotational energy must all be taken into account (AKA Hop-up / Bernoulli's principle). My guess is that with increased BB mass will result in less angular velocity (backspin).
-What does all this mean in a practical sense? Hell if I know!
A larger sample size as well as actual distances would be much more helpful! The low sample size might be the cause of the .28's not following the trend.
For those of you thought "WTF is a Joule?", here's some more calculation basically supporting the above. Below is the Difference in Velocity / Difference in Mass
(with .2's used as the standard to compare the difference):
.25 - 722
.28 - 803.8
.30 - 726
.36 - 648.8
.43 - 549.1
-Note the trend is for the numbers to decrease - except for the .28's.
-There is no linear relationship between change in velocity and change in mass (ie. You almost double the mass - compared to a .2 - by using a .43g BB but you do not cut the velocity in half). Which is why energy comparison is used (KE = .5 X Mass X Velocity^2)