You'r right I hate pulling the hammer for every shoot, I failed to make it semi auto.
Can you just regulate your pilot to have more flow or just release the pilot regulator (max output) just to see if the problem is caused by your pilot valve?
I failed with my semi (piston and hammer valve combination) since anytime the air from the pilot is used to push the hammer back (which is successfully push it back) the piston just won't open or just get the fssss and when I let this air free - still with the same hammer strength, piston size and pilot area size - the piston work well with the bang. It came to my conclusion (especially me with low pressure), it is better to let the air from the pilot running free without any task for it for the sake of piston opening efficiency.
i choose qev cuz i is a lot more powerfull( i also got a 6 mm hammervalve)
thank you, you rise my confidence to start building a small bore piston valve gun, I always worry if it would be no better that just a hammer valve gun.