SPA/ Airmax PCP Pistol tuning?

1. RESTRICTOR SCREW. Locate the grub screw in the top of the rotating breech block. This is your restrictor screw. It can be used to restrict airflow from the valve to the pellet. Open it up until it's not restricting the path...just bring it back flush with the surface. The only reason we need to use it is if the velocity is higher than we want and for some reason we can't get the regulator set low enough to achieve the desired velocity.

2. HAMMER SPRING ADJUSTMENT. Remove the handle (two screws through the sides up near the breech block, and one in the bottom). Turn the now exposed nut clockwise to increase spring preload (increase velocity), or counterclockwise to reduce it. Using your chronograph, increase preload until the velocity no longer increases.

3. REGULATOR ADJUSTMENT. If the velocity is lower than you wanted, increase the regulator setting. Go a quarter turn clockwise with an M4 hex key. Now go back to step 2 and find the new maximum velocity. (Or if your velocity was already higher than you wanted, back off the regulator and go back to step 2).

Repeat steps 2 & 3 until you're about 30fps above where you want to be, then make a couple of minor adjustments to improve consistency and efficiency:

4. Back off the hammer spring until the velocity falls about 20fps.

5. Thread in the restrictor screw until the velocity falls about 10fps.

No problem, good luck with it. Please be aware there are about as many people whose regulators don’t work properly as there are those that do. Unfortunately we haven’t found a clear cut root cause. I finally got mine to produce a stable velocity but it was more persnickety than any other regulated gun I’ve worked on. Creep can also be quite significant on some, to the extent that careful tuning won’t eliminate its effect. Some guys have installed an aftermarket regulator. I’ve resisted due to the cost and the fact I use it only at short distances, but I can see the justification for it because it’s one of the least pellet fussy guns I’ve ever used and accuracy is good enough for brain shots on small game out to at least 40 yards, provided you can aim steady enough. Really need a shoulder stock for that.

This little pistol in my opinion is the greatest bang for the buck out there. Bought one in .177 and had so much fun and good luck with it that I bought a 2nd. Simple to tune and the barrel still amazes me. The barrel looked terrible inside on the ones I received so took a brass brush and Hoppies and gave them a good scrub. After that at 10m sandbagged they would shoot through the same hole every time. Just amazing. The other thing that amazed me is the accuracy seems to stay the same no mater what pellet I feed it. Built wood grips and a shoulder stock for one. The one with the shoulder stock and a red dot is used for my shop gun. Out to 40 yards it's deadly on birds. The ones I have, have been trouble free. Like nervoustrig mentioned the regs are questionable in their adjustment but seem to work. I''m surprised these aren't more popular. sylvan

Before you adjust the reg. do you unload all air form pistol? thanks Willy