Chronograph results for 2240 valve extension

With stock valve stem, stock weight valve spring, and stock weight hammer spring. Valve has no porting or polishing. The breech is Cothran Machine with hollow bolt. Gun has a 12 inch barrel. Velocity Adjuster was unscrewed all the way, so no extra tension on the spring. Also used one of Anthony's Protops to test the gun with 12 gram cartridges.

Temp 65 degrees using co2 12 gram
14.66 grain Beeman FTS domed
CED Millennium Chronograph

535
529
530
540
533
533
529
530
523
525
525
525
523
520
515
506

I will be testing again tomorrow when it is warmer. I also replaced the stock stem with a polished ground down one. I haven't started porting the valve, and I am over 9 ft/lbs for at least 1 shot.