Valve Stems and Tanks?
Okay, I’m not the sharpest knife in the airgun drawer but do I understand correctly that the only difference in air output to the projectile is the hole in the valve stem given that the tophat settings are the same?
If so, how many flavors of valves are there? What’s stock and what’s not?
If it’s just a matter of swapping stems and barrels, then anyone could have anything, right?
Paul
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tis a lot more than a polished -ported stem to get a tuned valve.
itll give it a bit more kick anyways…
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Well your part way there in your understanding but your still missing some of the dynamics.
Part of what your missing is dwell time, or the time the valve stays open to send a longer shot of that air thru that wider valve.
Things like heavier hammers will make the valve open quicker and stay open longer, the heavier hammer can also be enhanced with heavier wire hammer springs and lighter wire valve return springs inside of deeper valve spring retainer.
Now due to the fact that AF valve return springs become a solid mass once depressed, you need to find a way around that mass, the quest for a smoother air flow can be aided by a tapered derlin valve seat.
Then once you have all that fixed, you can take advantage of that caverous valve stem and the valve staying open longer and increase the air pressure in your tank to 3000 and some go to 3200 and as high as 3400 but get a tank that allows a slightly higher fill safely. YOu can do this because your heavier hammer will now allow that valve to open against the higher pressure in the tank.
Having more pressure in your tank, realize most AF rifles shoot harder at 2800 than at 3000 PSI, simply allows more pressure to get behind that pellet and give you one or two more shots at the now faster dwindling air in your tank.
Now the top hat adjustment will give you more dwell time also, I usually adjust mine to the length of the barrel. Meaning no need to have that valve open when the pellet is no longer in the barrel and on the other side of the coin no need to have the air shut off when the pellet is only halfway down the barrel.
All of this willequal a higher velcoity and more FPE, so now you need to adjust all of this new dynamics to make your rifle more efficent, you do this by shooting over a chrony to get what is called a bathub shot string.
Now when your shooting your gun over a chrony to test your shot string, you may notice that your velocity starts high and goes straight down, to remedy this, you can adjust your PW to give lighter hits against the higher air pressure your using in your tank until your velocity string starts 10 to 20 FPS slow, tops out at the 20 fps higher velocity and then goes down in velocity as it rides the lowering air pressure in your tank untill your at the velocity you started with at your shot string, then you will have your improved more powerful shot string.
I am sure I missed al lot here so wiser heads will chime in, I hope.
I hope this helps,
Roachcreek