I got my P35-22 and P35-177 almost exactly 3 years ago. I put a different scope on the P35-22 today and started shooting it a little to zero the scope. I was getting 830+ on 21 grain at first and then it dropped to about 800. Sometimes velocity would go up with more hammer spring, sometimes it would not. This gun has consistently shot around 825 fps with these pellets since new. So I decided the regulator was probably acting up. I rebuilt two other SPA regulators this week. They were from used guns that are new-to-me. But how to do it was fresh in my mind.
I pulled the regulator out the back of the airtube, it conveniently was locked to the end fitting. Nothing looked bad but I replaced all the O-rings and put some anti-corrosion spray on the bellville washers, the kind Motorhead (Scott) recommends. Then I put it all back together replacing O-rings in everything I took apart. When I got it together velocity was low, under 800 so I correctly guessed the regulator was a bit high. I measured the height of the stem of the adjustment screw above the lock ring as best I could with digital calipers but I guess I was a bit off. So I turned it down a little over a quarter turn. Moved it maybe 0.3mm. Looks like success. Velocity was over 830 with the hammer spring at max and would presumably have gone higher if I had more hammer spring. I turned the hammer spring down over a turn and am getting consistent 820-825 velocity and accuracy seems to be there, maybe. I will tune a bit more. The first time I had it together with the new regulator setting it leaked. I think it was the O-ring under the gauge but I replaced all the O-rings in that end of the gun. I had not taken that apart intially but when I got that nut off and the gauge off the O-ring seemed to have no silicone grease on it. Dropping the pressure to zero a couple times probably finished the killing of that O-ring.
So my recommendation is if you have a SPA gun that is 3 years old or more and it starts acting funny it may be time to replace a bunch of O-rings including the regulator if it might be involved. I've messed with my other P35s a lot more, this is the first time the 22 has been apart. So I've replaced parts already in the others but this one shot so well I was leaving it alone. But hopefully now it will return to it's original form which includes excellent accuracy. Last 4 shots hit at least the 9 ring so it may be there if I can get the Veyron adjusted and read the wind well.
