I need to know the spring parameters.
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I can’t answer your question but if it’s regulated (aren’t all Crickets?) then the valve spring doesn’t make any difference. In fact you could remove it altogether. In this circumstance, all it does it hold the valve closed if you are filling from zero pressure with a hand pump.
Contrast that with an unregulated rifle where it plays a role in the varied lift and dwell that goes into producing a useful bell curve over a range of pressure.
So for your Cricket, just find something that fits and applies a couple of pounds of pressure to the poppet.
Contrast that with an unregulated rifle where it plays a role in the varied lift and dwell that goes into producing a useful bell curve over a range of pressure.
So for your Cricket, just find something that fits and applies a couple of pounds of pressure to the poppet.
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@nervoustrig, I was told by Ernest Rowe that the valve spring does make a difference. Case in point is when the Crickets are "power tuned" by adding the additional plenum space, a lighter valve spring and heavier hammer spring are also added, along with a metal hammer spring nut (adjuster). But what does he know...? 
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Haha, fair enough! ER’s recommendation takes it in the same direction I was describing...using a lighter spring. Ultimately when tuning a regulated rifle, adjusting the hammer spring tension to find the knee of the velocity curve will produce effectively the same result whether it is a stiff valve spring or a soft one.
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Slow (or fast) first shot is a classic sign of regulator creep.
The valve spring will have nothing to do with that symptom.
The valve spring will have nothing to do with that symptom.
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Okay for starters, let's define regulator creep. It is a slow rise of the regulator's output pressure. Generally creeping is caused by a slight imperfection in the valve seat.
Let's say the reg's setpoint is nominally 1500psi...but when the rifle is left idle for an hour (or overnight), it creeps up to 1800psi. In normal operation, when you fire a shot, the valve opens to allow air to flow from the high pressure reservoir over to the output side of the regulator (the plenum). As the plenum pressure rises, the regulator's piston moves ever closer to the valve seat until the flow of air is halted. That means the last little bit of pressure rise is happening through an infinitesimally small gap. If there is an imperfection like a small scratch or a worn spot, air will continue to slowly seep past the valve seat until the pressure finally rises to the point where it pushes the piston (metal) sufficiently hard against the valve seat (plastic) to compress it to the point where it completely seals off. In some cases that may take hours.
So how do you deal with it? Well, the first thing to do is confirm the rifle is adjusted to operate just below its peak velocity. Keep increasing hammer spring preload until the velocity no longer increases. Then reduce the preload until the velocity is about 97% of that maximum. So let's say you found your max velocity to be 900fps. What you'd do is back off hte hammer spring until it falls to about 973fps. At this state of tune, it will be less susceptible to velocity variation...much like an unregulated rifle maintains a tight velocity spread over a wide range of operating pressure.
If that doesn't remedy the first shot problem, it suggests the creeping is pretty severe and you'll have to turn your attention to the regulator. If it's new and in warranty, I'd say send it in for repair. Or you can see if a rebulid kit is available, the important part of course being a replacement valve seat. Or if you are handy, you can disassemble and inspect your regulator, and dress the surfaces to remove whatever defects you find. Usually what I find is that the plastic seat has become worn and irregular from repeated cycling, or has been scratched by a piece of foreign material.
Good luck!
Let's say the reg's setpoint is nominally 1500psi...but when the rifle is left idle for an hour (or overnight), it creeps up to 1800psi. In normal operation, when you fire a shot, the valve opens to allow air to flow from the high pressure reservoir over to the output side of the regulator (the plenum). As the plenum pressure rises, the regulator's piston moves ever closer to the valve seat until the flow of air is halted. That means the last little bit of pressure rise is happening through an infinitesimally small gap. If there is an imperfection like a small scratch or a worn spot, air will continue to slowly seep past the valve seat until the pressure finally rises to the point where it pushes the piston (metal) sufficiently hard against the valve seat (plastic) to compress it to the point where it completely seals off. In some cases that may take hours.
So how do you deal with it? Well, the first thing to do is confirm the rifle is adjusted to operate just below its peak velocity. Keep increasing hammer spring preload until the velocity no longer increases. Then reduce the preload until the velocity is about 97% of that maximum. So let's say you found your max velocity to be 900fps. What you'd do is back off hte hammer spring until it falls to about 973fps. At this state of tune, it will be less susceptible to velocity variation...much like an unregulated rifle maintains a tight velocity spread over a wide range of operating pressure.
If that doesn't remedy the first shot problem, it suggests the creeping is pretty severe and you'll have to turn your attention to the regulator. If it's new and in warranty, I'd say send it in for repair. Or you can see if a rebulid kit is available, the important part of course being a replacement valve seat. Or if you are handy, you can disassemble and inspect your regulator, and dress the surfaces to remove whatever defects you find. Usually what I find is that the plastic seat has become worn and irregular from repeated cycling, or has been scratched by a piece of foreign material.
Good luck!
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