What does the chamber look like on these things? You should be able to tell from the photos but here is a simplified diagram of the internals: https://i.imgur.com/Iu04Ne8l.png Green arrow shows where the air is filled from, this is then closed off and another valve is opened at the red arrow to emp...

Most of the pneumatic projects on this forum use dump valves that essentially empty the chamber for every shot. Semi-automatics based on quick exhaust valves piloted by 3 way valves look something like this: https://i.imgur.com/JW8LrsI.gif A main chamber feeds a firing chamber, with the latter being...