Several good points have been raised so far about aperture size, creep versus slow fill rate, etc.
I read the review you’re referring to and I think we may as well identify the make and model as being the SPA PP700S-A because it has a few unusual issues compared to most other regulator designs that bear calling attention to.
One is that the Belleville washers are a small diameter with relatively little travel compared to more common regulators I’ve encountered. That has the potential to cause a slow refill because the valve seat doesn’t open very far.
From the factory, they are arranged in a 2P 5S arrangement (( )) (( )) ((. I decided to reconfigure mine to a plain series arrangement of 9 () () () () ( which almost doubles the travel. Note it also halves the spring rate which means I can’t achieve as high of a setpoint but that was fine for my purposes because I wanted to tune to around 600fps for a longer shot count. Sorry, I did not explore the limits of adjustment so I can’t comment on how this arrangement would support other states of tune.
A second issue is related to the valve seat. It is formed by the conical underside of a screw meeting a tapered opening in a plastic washer. That creates a fairly large area which has to mate so perfectly as to prevent very small and highly motivated molecules of gas from getting by. I attempted to lap mine together to deal with it. Twice. It’s a fidgety thing because the parts are so small so I finally decided to just flip the washer over so the screw could mate with something more closely approximating a knife edge. That simple change focuses the applied force onto a smaller area and makes it easier to form a positive seal between them.
But you may wonder why I am talking about creep in the context of a slow fill. Well, in this particular case, the author was describing it taking 2 minutes to refill. That time scale elbows its way into the realm of creep.
Lastly, a third issue relates to how the high and low pressure sides are separated by a crush seal where the same plastic washer is squeezed between the two halves of the regulator body. It is extraordinarily difficult to get it to seal properly when you reassemble it. Even with a custom-made tool, I could not develop enough torque to keep it from leaking. It was a well-known problem and there was a simple fix published to simply drop an O-ring into the pocket before threading the regulator back together.
That’s all well and good. It keeps the air from escaping out into the world, but what hadn’t been considered is what effect did it have to the operation of the regulator. Well, now that the air is trapped inside, it squirms its way around the washer and into the plenum, causing the pressure to slowly rise until it finally gets high enough to push the head of the screw down hard enough to cause the underside of the plastic washer to seal against the regulator body and halt the flow of air that’s been seeping under it. Supergluing the disc in place remedied that problem in mine.
All told, it was definitely my most challenging regulator ever but I’m pleased to say it now exhibits no creep and the fill rate is faster than I can load the next pellet.
