I'm in the process of tweaking my 2560 HPA.... nothing major, just seeing if I can get a squeek more power (like 46 FPE isn't enough!), and more shots by changing to an 18 CI tank instead of the 13 CI, still regulated to 1600 psi.... The smaller tank is moving over to my 2260 HPA which is getting a reversed tank block like the .25 cal has now.... I'm hoping that the much larger plenum (the entire 2260 tube) will give me the same power (36 FPE for the .22 cal) on 1600 psi as I was getting on 1800 with the small volume between the regulator and valve it has now.... Here are the new parts I've made....



I made an extended valve front end to move the O-rings in front of the roll-stamp on the 2260 tube.... It has a lot larger bore, and is 9/32" at the spring seat instead of the stock 1/4".... The valve spring has been enlarged at one end to 9/32 to increase the flow as well.... The rear half of the Disco valve is bored out to 5/8" ID (from 1/2") to unshroud the poppet.... The flow into the valve is so much larger than out, basically the valve volume is the whole 2260 tube, from a pressure drop point of view.... I thinned out the stem of the valve poppet from 0.157" to 0.109", shortened it 0.100" for increased hammer travel, drilled the throat of the valve to 1/4", milled the exhaust port to 3/16" on a 20* angle, and rounded the corners for better flow....

The hammer has been modified by grinding a flat on the bottom to allow for the extra travel without hitting the sear.... and the cocking slot in the tube lengthened 0.100" as well.... I made a spring guide from steel which sits in the hammer and adds 11 gr. to the weight, the total is now 68 gr. instead of the stock 60 gr.... The spring guide runs in the preload adjustment screw, and provides a cocking indicator as well.... Thanks to Ribbonstone for that idea....



The tank block is the reversed style I came up with a while back, and mounts to the threaded front of the 2260 tube using a drilled out CO2 nut riding on a hollow bolt.... The aluminum bushing carries an O-ring to provide a seal past the threaded area where the tube is full thickness.... O-rings (not shown) between the parts seal everything up.... The lower part of the tank block carries a standard regulator with the bottom of the tank back towards the trigger, and right up against the bottom of the 2260 tube.... The tank acts as the forestock.... In the bottom of the block is a 3-groove Picatinny rail for a bi-pod, sling-swivel, flashlight, or laser.... On top of the tank block is mounted the barrel band.... The vertical air passage is sealed on the bottom by a 10-32 low-profile SHCS carrying an O-ring.... If desired, I can drill and tap a 1/8" NPT hole on the side of the block for a gauge to show the pressure in the plenum....

This valve is also a prototype for a .25 cal pumper I plan to build in the near future.... The port areas exceed 3/16" diameter at all points.... and is the largest I have gone starting with a Disco valve.... It can be fitted with a gauge by leaving a thicker wall in the appropriate location.... and of course a pumper version will need a check valve in the front.... The pumper version will have a volume of about 5 cc....

Bob