I made a new valve front end today to incorporate the gauge block and increase the diameter of the through hole.... I moved the O-rings to in front of the gauge hole so that I wont have to deal with shredding O-rings as they pass the hole in the tube for the gauge.... Even though it's deburred, it's a PITA to keep the O-rings stuffed deep enough as they slide past.... so now I don't have to worry about it.... While I was at it, I shortened the threads by 0.20" to help open up the flow inside of the valve....



One of the choke points was the hole in the spring seat in the valve front end, and there is little point in drilling it out because the spring is just over 1/4" ID.... Sooooooooo, I tapered the spring.... I used progressively larger drill bits, inserted the shank end into the spring, and tapped the spring with a hammer on an anvil to increase the diameter.... I ended up with a spring that is stock at one end to fit the valve poppet, and 3/8" OD x 19/64" ID at the other end.... I stress-relieved the spring afterwards by heating it at 500*F for 1/2 hour.... The larger spring ID meant I could drill the valve front end out to 19/64 which increased the area for airflow into the valve by 41%.... Compared to the restricted flow through a stock gauge block (1/8") it's an increase of over 5 times.... The valve now has 2.5 times the area on the inlet end than on the exhaust end.... so the entire reservoir can keep the pressure up in the valve during the shot cycle....



Other mods include drilling the valve throat out to 1/4" (from 7/32") and thinning down the valve stem from 5/32" (0.157") to 0.115" The exhaust port in the valve has been opened up to just over 3/16" (from under 5/32") and angled 20 degrees and streamlined.... The new ports are 70% larger than stock and a much more direct path.... I also bored out the inside of the valve to 5/8" (from about 1/2"), not so much to increase volume as to unshroud the head of the valve poppet and ease the passage of the air around it.... and shortened the threaded area as well.... The threads are in compression, all they really do is hold the two halves of the valve together to seal the O-ring between the halves.... so strength is not really an issue there.... The tightest restriction in the whole system is the exhaust portion of the valve, everything else has greater flow areas.... I also shortened the valve stem by 0.090".... It now barely protrudes from the end of the valve when the spring hits coil bind (which limits the travel).... and the increased hammer travel will allow the hammer to have increased momentum when it strikes the valve....

All in all, I'm pleased with the progress and look forward to reassemblling the gun with the new valve parts.... Once those trials are completed I will likely work on a new hammer....

Bob