Non to light valve spring by Cygnus-x

Found this in my notes, originaly displayed on TOG sight.

Cygnus wrote,
ok heres first edition of my no spring guide

Step by step guide to a very light return spring/no return spring at all

The goal is to have a valve that is easy top knock open, produce more power and will not stay open dumping the air until pressure gets low.

1. Remove valve from body remove spring retainer replace spring or just remove retainer and spring all together, and pump the bottle to the lowest pressure your going to be shooting at. I don’t go lower then 80 bar so that’s what I will be using as a reference for this guide.
2. Turn the power wheel to its max, and turn the tophat to it closest position to the bottle giving it as little travel as possible.
3. pump the bottle to approx 90 bar, this leaves room for some shots before the pressure hits 80 bar
4. Now take a shot if it fired ok go to step 5, if it dumped turn the powerwheel down, refill bottle and repeat
5. Turn tophat out quarter to half a turn, in the beginning you can do half turns towards the end when fine adjusting you can try with quarter turn, fire the rifle….keep doing this until the rifle dumps…keep bottle pressure above 80 bar so make sure to check on that every 3-5 shots or so. If you notice pellet speed stops rising, your where you wanna be and no need to continue till It dumps
6. Once its dumps the same place most times turn the tophat back quarter to ½ a turn. I suggest you write down how many turns the tophat is out
7. this should be the setting for max power, and you can now try to lower the powerwheel to get the setup more consistent, wasting less air amd get the noise down, the powerwheel will be much more effective now

And now for the explanation of it all

have you ever tried to block the drain in the bathtup with your hand, and you will have noticed that your hand is being pushed by the pressure having a self sealing function, This is the same that is happening in your talon bottle…the huge pressure is trying to push out of the bottle and it is pushing on everything in it way, the stem and delrin is in the way and it cannot move other than back and forward…and with all that pressure behind it its not going backwards by it self…and as soon as the pressure from the hammer has dissipated the valve will try to close it self, this is why no spring is needed.

Since there’s no spring the valve is dependent on the pressure to close it, when this gets too low the hammer and mainspring will be able to hold the valve open and it will dump, the cool bit is that the valve is no longer controlled by the valvesprings force to close but the pressure in the bottle, and the lower it gets the more the hammerspring and hammer can hold it open self regulating the rifle effectively with short duration high pressure bursts and longer burst of lower pressure….

All shots should be carried out over a chrony to see what’s going on….when I did the final step, of turning the powerwheel down, I found the noise to go down quite a bit but power staying pretty much the same, my rifle was shooting at 830 with 42 grain EJ .25 cal, at max preload it did 850, but at 830 fps the noise was down a lot, and consitency is up….the rifle now shoots a whole tin of EJ going from 830 to 840 where it tops out and down to 830 again over 30+ shots and it keeps going till the tin is empty and its doing 760 at that time, similar results can be had with turning the tophtat in towards the bottle too….while turning this out