Tactical Trijicon ACOG TA01 Style 4x32 Cross Sight Rifle Scope + Kill Flash
TROBB Solid Aluminium Dovetail Power Block with Gmac hollow probe and G-mac Bolt
Gmac Brass Power Adjuster Spring And Guide/Drilled Out Standard Valve For more air space
Hammer Mods//Gmac 30% Lighter valve Spring/Gmac Brass Safety Catch//Transfer port drilled out
Full Gmac Trigger kit/Gmac barrel cut to 9inch/Weihrauch Silencer/Custom Home Made Grips/
New TRACER LEDRAY GL2 LAMP 90m Range Beam//HI-Pac
...during the firing cycle, there must have been a significant fraction of the total volume of the air charge between the piston crown and the port before the valve opened.
So, whether the piston moves or not, the effect would be the same. If the port is so restrictive as to interfere with that fraction of the charge doing its share to pressurize the bore and push the pellet, velocity will suffer. No?