Have you shortened the threaded section of the of the valve body? You can shorten it to about 0.375" above the shoulder where the o-ring is sandwiched.
The valve body bore can be bored out to 0.475" to allow more air flow around the pop-it valve head.
You might want to try a search and see if you can find anything on the subject by Rich from Michigan. I know he has done a few big bores (.308) based on the QB with a modified stock valve that have produced about 100 fpe.
''If everything seems under control, you're not going fast enough!'' Mario Andretti
This message has been edited by VWDan on May 28, 2012 7:20 AM
JK's Airgun Forums, moderators, and administrators are not responsible for any problems that may occur from reading or using content posted on this forum, as they are the exclusive responsibility of two parties: the person who posted it and the person who acted on said posted information.Use of our forums by people under 18 years old is allowed only with legal guardian(s) present..