Last year I made a regulator that attaches directly to a Disco valve.... I was working on different ways to produce a non-PAL PCP (ie under 500 fps).... It did the job by using a shortened 2240 valve spring.... Here's what it looks like....



It replaces the front end of the valve, and is long enough to cover the roll-stamped area on a 22XX tube.... I used the piston and spring from a Ninja regulator, so the parts are easy to obtain, in fact I just bought a Ninja rebuild kit to get them.... The back half of the valve, including the poppet and spring, are stock....



I installed it into a 2260 tube for testing.... I found the velocities more consistent with a lightened hammer (I went all the way to 30 gr. - 50% of stock).... Here is the shot string....



It appears that the regulator setpoint with just the spring (no shims) is about 650 psi.... I was quite pleased with the flatness of the shot string, 55 shots averaging 492 fps with 14.3 gr. JSB Express pellets, and the efficiency worked out to 1.21 FPE/CI.... I also tried it with a stack of Belleville washers (disc springs), and with a setpoint of about 1350 psi it gave 10 shots averaging 773 fps (19 FPE) with an efficiency of 1.13 FPE/CI.... The limited number of shots at higher power is because of the 2000 psi fill limit.... It only left 650 psi available, which is only 168 CI (at 1 bar) with a 2260 tube.... You could double that shot count by using a Disco tube.... but in reality there is little point.... Regulators are at their best when the setpoint is low enough to utilize a much wider range of pressure.... Having said that, shimming the coil spring a bit and bringind the setpoint up to about 1000 psi should give a good shot count and velocities in the high 600s.... Adjusted the way it is would produce a non-PAL Disco with over 100 shots per fill....

Bob