I have trouble with velocity, I can't get it over 220 or so. The same valve shoots fine on an ULE body. I also have the ring installed, but I was already having that problem before the ring. Valve too far back you say? Did he have you measure something?
My lvl10 engages every 5 shots or so while dry firing, I think in my case it is catching on either the ring or the body itself. Do you have lvl10?
I wonder if our problems are related or not. I have read on AO of someone needing to dry fire a few tanks before it would get decent velocity.