I grabbed these images from an airgun forum. They aren't adding length - those are CB9 valves - they're removing the exterior wall of the Sheridan cartridge valve to increase the total gas available when the valve opens. Stock Sheridans have tiny little chambers, and PPS even opens them up when they make their scratchbuilt guns. This is just a dead simple way of increasing volume in a cartridge valved gun.
Originally Posted by agentSmith
oldschool play is about sportsmanship and respect, oldschool gear is available on Ebay.