django wrote:In what way do you mean streamlining the valve??.
Mass produced valves usually make concessions to ease of manufacture which means they are not necessarily the best shape for best performance, and you can trim them down in order to improve gas flow.
For example, here are some mods which can be done to the Crosman 22XX series:
http://www.airgununiverse.net/22xxvalve.html
The stock barrel is sadly just smoothbore, but if the machinist guy we use at work will do it i'll get a longer barrel made up which should increase performance a lot .The standard barrel on the CP99 Compact is only a pathetic 3.6" long so I'll try get a 6" Barrel made up.
If you're firing steel BBs, you don't need rifling anyway. A longer barrel will improve performance and reduce noise, and it gives you an excuse to add a suppressor
Cant take pics of the stone filter cause I broke the camera

its just a tiny stone filter that sits in the co2 bulb Puncture tip.
I doubt removing it will improve performance, usually the gas for the individual shot comes from an expansion chamber past the filter, not from the capsule itself.