Others What is valve lock?

[igolfat8]

I’ve got a 22 Atomic and wonder if I had valve lock? It was acting really weird. Regulator is all stock setting about 125ish. I had the transfer port on the lowest setting and the HS was backed out 35 clicks from full in. Shooting JSB 15.89s and the speed was really erratic jumping from high 400s to 600. It would shoot in the 580s for a while then fall way off in the high 400s then bounce back to near 600 With no regularity.

I had been shooting CPHPs with this tune but speed was erratic with 40 fps spreads but not near as bad with the 15.89s. So for giggles I maxed out the HX to full in, put the transfer port on high and had consistent 720’s with 15.89. Put the transfer port on low and the speed dropped to 595 with a spread of 18 and SD of 5.5 and stayed consistent for 60 shots.

So, with the very light HS setting would this have caused the erratic speeds and was this valve lock?

 

[pan60]

when you have enough pressure in the valve that the hammer cannot hit hard enough to open it.
locked

 

[Bladebum]

I’ve got a 22 Atomic and wonder if I had valve lock? It was acting really weird. Regulator is all stock setting about 125ish. I had the transfer port on the lowest setting and the HS was backed out 35 clicks from full in. Shooting JSB 15.89s and the speed was really erratic jumping from high 400s to 600. It would shoot in the 580s for a while then fall way off in the high 400s then bounce back to near 600 With no regularity.

I had been shooting CPHPs with this tune but speed was erratic with 40 fps spreads but not near as bad with the 15.89s. So for giggles I maxed out the HX to full in, put the transfer port on high and had consistent 720’s with 15.89. Put the transfer port on low and the speed dropped to 595 with a spread of 18 and SD of 5.5 and stayed consistent for 60 shots.

So, with the very light HS setting would this have caused the erratic speeds and was this valve lock?

No not valve lock, as explained above by @pan60 , what you are seeing is out of balance hammer spring to reg pressure ratio. Very common, some regs are extremely sensitive, others have a wide range. Why it happens is because the regulator can not detect the small amount of air taken from the plenum fast enough, so it does not open to refill the plenum.

 

[rsterne]

PCP valves operate in "partial valve lock" a lot of the time when properly tuned.... What I mean is that the hammer strike is tuned in such a way that the valve does NOT open fully.... A valve opening fully generally means the gun is wasting air.... Complete valve lock, where the hammer can't open the valve at all, is rare, and generally increasing the hammer strike solves it....

Bob

 

[igolfat8]

Thanks for that reply Robert. How can you really tell how far the valve is actually opening without using X-ray vision? Not trying to be a wise guy but trying to learn and understand.