Feedback from many dozens of customers has been 100% positive. Only two were ever returned: one was due to an alignment issue with the threaded hole not exactly 180 degrees from the exhaust port. Easy fix! The other had a tiny spec of swarf at the check valve. Another easy fix.
BUT... there is barely a day that goes by that I do not get questioned by prospective owners because they haven't read this blog I am typing now! LOL
Lets start at the beginning. I maintain that the longstanding fully modded flat top valve and its companion flat top adjustable piston is not one mod, but actually two. The flat top of the valve and the mating flat top of the piston has NOTHING to do with the power potential of the valve. The flat topping business is ALL ABOUT making the physical pumping efficiency so that a user can get more air per stroke into the valve. Not a bad thing at all, but it does require BOTH parts (more expense and adjustment required) to get it. I make, sell and use the flat top pair when I want BOTH more efficient pumping and a valve with more power potential.
So what if one were to take a bone stock (un-modded) valve and flat top the face of it... then pair it with a flat top adjustable piston? What would we have? It will take less pumps to reach the "sweet spot" (please read earlier blog)... but it will shoot the EXACT SAME fps as the stock valve and piston that took more pumps to reach the sweet spot, The flat top is for pumping efficiency but does nothing to make the valve ultimately more powerful. So we would have to pump less to get the maximum power from the stock valve, but the performance would not be enhanced at all.
Let's go the RP direction. What if we leave the piston stock, then take a bone stock valve and modify it to make the pressure chamber slightly larger in volume... and then make the exhaust chamber slightly larger in volume AND angle the port? Now the pressure chamber will hold more volume of air. It will take MORE pumps to bring that larger volume of air even to the same maximum PSI as before the valve was modified, but now when we reach the "sweet spot" ... stop pumping and fire the gun... a larger (and more powerful) volume of air can be released from that larger pressure chamber and exhaust a larger charge to the barrel port for higher fps (and fpe). Yes, we had to pump more times, but we get more powerful performance results.
We (and our customer users) have proven that this works very well, costs less, and is easier to accomplish.
Other than having to pump more times to reach the sweet spot, is there any downside to this? Maybe, depending on the operator. If someone pumps 20+ times every time they fire... and pumps quickly,,, and shoots many times and often,,, then the stock plastic piston with its rubber cup is going to wear quicker. I have not seen one break. I have not even been able to wear out a piston cup yet. But lets say that this speed demon that shoots an entire tin of pellets every outing... and shoots every time they get a chance... experiences a negative change in the gun's performance after many weeks/months/years (who knows?). What is the downside? Another new stock piston and cup is cheap and easy to replace. The valve, tube and linkage should be fine.
Bottom line for me: I have a couple of guns with this valve and I like what it does for me with the way I shoot. If I am plinking or target shooting (90% of the time) I do not pump for maximum velocity. If I am shooting for power / speed then I know I have that capability. When I do pump that many times I do not fiendishly pump because I am not racing to shoot again and I can feel how warm the tube gets when I have done that in the past.
For some actual chrony data from one of my customers that has two of these (one in a 1322 and the other in a 1377), please see the "Kind Words" page and the long entry there.
Just remember to "Have Fun Shooting"!