Hey Batman, thanks for the response! I don't ever fill beyond 3000psi so I don't think that is the issue. I thought of the breech seal also so I took it out. It looked fine so I tried to put it back. That is a tight space for my sausage fingers! Thought I had it in so I went to test the pistol again and velocity was even lower. Looked in the breech and the o ring was gone. I guess it wasn't in correctly. I assume it just blew out the barrel. I'm now trying to order some new breech o rings. The barrel is tight. If you want to, how tough is it to remove the barrel on this thing? It's very hard to find any instructional videos on the subject but it would sure make o ring replacement easier! Love this pistol but seems like a pain in the neck to work on.