Today I drilled out the transfer port hole in the Disco tube to 5/16", and while I had it mounted in the mill I lengthened the front of the cocking slot for the hammer by 0.20".... I will be increasing the hammer stroke, and just wanted to make sure the cocking pin won't hit the end of the slot on firing.... I then deburred all the slots and holes, paying particular attention to the gauge hole, which makes a great cheese grater the way Crosman machine it, but not very kindly to the O-rings you have to slide past it.... I pay particular attention to the front and especially the back inside edge, rounding it so that the O-rings can slide past it without getting torn.... Not doing that the first time you have a Disco apart is a big mistake.... I then carefully cleaned the inside of the main tube....
I mentioned before that the bands I got from Lloyd that hold the tubes together were for a BNM breech with 1" shroud.... The upper portion has an O-ring groove machined into it for a #022 O-ring, that will hold that diameter shroud.... I will be using only a 7/8" OD shroud, but I found that by using #212 O-rings I could used the same bands, as they have the same OD but the smaller ID I require.... However, the groove in the bands was too narrow, so I chucked them I my lathe and put a taper on the side of each groove so that they were 0.140" wide at the inside, in sort of a half-hexagon shape.... I did NOT have to cut the groove any deeper, just wider at the inner edge.... With a 70D O-ring installed, they fit the 7/8" tubing I have nicely, a snug, sliding fit with the O-ring compressed about 0.010".... This will hold the shroud well, without being rigid.... and there is no way the O-ring can pop out once the tube in installed....
I checked the fit of the valve, ground a notch in the top rear to miss the forward breech screw location, and also ground a notch in the bottom rear to allow better venting of the space between the hammer and valve through the hole behind the bottom screw.... I then disassembled and carefully cleaned the valve, lubed the stem and O-ring and put it back together.... I then lubed the valve and gauge block O-rings, slid the valve into place, installed the 10-32 screws, then installed the gauge port and a 3000 psi gauge.... As the O-rings pass the gauge hole, be VERY careful they don't get cut.... I use my fingernail, or a small flat-bladed screwdriver, to coax them past my nicely rounded edge, but you still need to be careful and work slowly.... I rolled a #016 O-ring onto the upper plug of the Disco Double kit, where it butts against the end of the main tube, lubed the O-ring that seals inside the tube, and screwed the tube onto the upper DD plug that contains the regulator.... Just before it contacts the O-ring, have a look at where the gauge is in relation to the lower DD tube, and stop threading it on when the gauge lines up with the lower tube and the O-ring is under the least compression possible.... Its only purpose is to fill the gap between the end of the upper tube and the upper plug for appearance and to keep the dirt out.... There is plenty of thread engagement without cranking it that last turn and squeezing the O-ring out of the groove....
I then temporarily installed the trigger group so that I could align the position of the lower tube with it.... I slid the narrow tube band (the one without the Picatinny rail) onto the two tubes, right back to the end of the lower tube, leaving only the flange on the aluminum plug past the band.... Once I was happy with the alignment of the tubes I snugged the setscrews on the bottom of it, turned the assembly around and viewing from the front made sure the tubes weren't twisted and sat parallel with each other.... I then tightened the setscrews in the tube band, being careful not to tighten them so much they would crush the tube, which is thin there because that is where it is threaded.... This completed the pressure assembly, and it now looks like this....
At this point, it was ready for a leak test.... I slowly put in 1000 psi, and checked for leaks with soapy water on a small brush.... Finding none, I the gradually filled the reservoir, 200 psi at a time, allowing for the pressure to equalize and kept my eye on the gauge, which reads the pressure downstream of the regulator, so it will tell you the setpoint.... It stopped and held at 1600 psi, so I stopped filling at 2000 psi, waited a few minutes to be sure it hadn't crept up (it hadn't budged), and since I was still attached to my Great White I bled the line very slowly, which will often leave the check valve in the Foster open and allow you to bleed air from the bottom tube.... It worked, and once I got the tube down to 1400 psi I checked the gauge on the gun, and it still read 1600 (as it should).... I then quickly bled the air from the line to my tank, leaving 1400 psi in the lower tube and 1600 in the upper.... I wanted to increase the setpoint of the regulator, both because I expected to need a bit more pressure for this project, and because I wanted to play with the adjustment.... That meant that I had to bring the pressure in the upper tube down to less than the current setpoint, so I didn't damage the HP seat in the regulator....
The only way to do this, or at least the easiest way, was to fire the gun, so I temporarily installed the trigger group, a hammer, spring, and RVA, and making sure the transfer port was facing away from me, pulled the trigger.... I wish I had rembered to remove my hearing aids and put in my ear plugs, because it was LOUD!.... Fortunately, my hearing aids have a "clamping circuit" that prevents loud noises from getting through, so the actually act like (rather noisy) ear plugs.... Just the one shot dropped the pressure to 1400 psi, so now both tubes were below the current setpoint.... Since I was going to increase the setpoint, I didn't need to remove any more air.... If I had been going to lower it, then the pressure in both tubes would have to be lowered BELOW the new setpoint to make sure you don't damage the HP seat.... To increase the pressure you have to move the seat OUT, towards the front of the gun.... This allows the piston to move further before closing the HP seat, which compresses the Belleville springs further.... That takes more force, which means more pressure, and you end up with a higher setpoint.... To lower the pressure you need to do the opposite, you need to move the seat IN.... If you didn't bleed air from the gun, then you would be screwing the adjustable metal seat into the plastic seat on the end of the piston, and could easily damage it.... To repeat....
Adjuster OUT (CCW) increases the setpoint pressure.... Adjuster IN (CW) decreases the setpoint pressure....If the screw is hard to turn, you probably forgot to bleed the pressure down, STOP and make sure both tubes are BELOW the lowest pressure setpoint you need.... The slot in my adjuster, viewed from the front, was at about a 45* angle, from 10:30 to 4:30 o-clock.... I decided to try 1/8 turn CCW, so I set the slot horizontal, at 9:00 to 3:00 o'clock.... The screw moved with noticeable drag from the O-rings that seal it, but was not difficult to adjust.... I then reconnected the Foster to my Great White and added 200 psi at a time, watching the pressure gauge to see how much I moved the setpoint.... It was almost exactly 200 psi, it now settled in and stayed at 1800, which is pretty close to where I think I need it.... certainly close enough for initial trials.... I continued filling the lower tube to 3000 psi.... let it sit for a while to cool, and topped it up before coming in to take the photo and write this post.... The assembly will sit under pressure while I continue to work on other parts of the gun as a leak test.... Note that if the gauge eventually shows a pressure drop, if would indicate that the leak is downstream of the regulator.... If there was a leak upstream of the regulator, the gauge (in theory) would not give you an indication of that.... However, the next time you went to fill from a tank, you could hear the check valve in the Foster click below the pressure you left the gun at....
Bob