Originally Posted by Styrak
Different barrel lengths and how your hopup contacts the BB also affect it. If you have a gun with the same barrel and same length and same/similar hopup you'll get most likely get very close to the same results. 30 FPS going from .20 to .25 seems right. That's what I got with my AUG with stock TM barrel. Notice both your guns changed by 30 FPS.
Also, BB mass % won't = velocity %.
And gas guns are a whole different deal too.
Yes, I know. So why then do velocity changes drift so wildly for so many different guns? You answered the question already, and it boils down to my original point that not all guns are consistant. I was correct and you just reiterated that.
I go to my CQB PTW with the exact same cylinder, identical hop-up and the velocity increases about 8%.
So, unless you can build a formula that takes into account every length of barrel with every type of chamber with every type of hop-up rubber with every weight of BB, then my point still stands.