the Problem with SweetSpotting
when you sweetspot a Sniper you run the lightest mainspring tension and highest psi for your valve and valve spring, thats fine for a semi because either the hammers get cocked mearly seconds after it strikes the valve farting very little its not noticeable, like with a cocker, or in the cases with most electronic open bolt paintguns, the dwell time is precise and is air driven.
but with a pump you have a long dwell that is driven by a spring, and when the hammer strikes the valve the spring is at its weakest, and the hammer is now able to be pushed back by valve causing hammer bounce.
and with most lightly sprung cockers that chrono a full 300fps when you put a pump kit on them and fire you get some crazy hammer bounce.
so on to the Article!
well theres 2 things we call farting, one is hammer bounce the second is venting.
Hammer Bounce is when the hammer hits the valve stem is bounces up then hits the valve again, opening it repeatedly for a short while.
to cure this you need to reduce the energy hitting the valve the 2nd time so it cannot open up again,
so you can put in a harder(850 & up) valve spring or lighter(350 & lower) depending on your psi, reduce your hammer weight, reduce your psi, or increase your main spring tension. Or get your degree(infomercial joke). Or a combination of them all.
CCM's valve had this problem, to stop it they switched from a Delrin cup seal, because it was so hard it reopened very easily, to a rubber cup seal that with its softness made it harder to reopen. Also they Lengthened the stem length, so the main spring is compressed when it bounces back, reducing distance the hammer bounced back.
i wouldn't try this unless you REALLY know what your doing and have an extra stem.
the other Venting, happens when your dwell is too long, in other words when you valve is open too long, this can range from a farting sound to the gun just venting air after every shot
to stop this you can put in harder valve spring, increase your hammer weight, increase your psi, or lighten your main spring tension. Or get your degree(infomercial joke). Or a combination of them all.
as you can see going to extremes on either side of this balancing act will result in farting either the Bounce(true farting) or venting, Except in the case of putting in a harder valve spring, but it can lead you to increase your psi and reducing psi making it fart yet again, so you would need to put in a heavier main spring as well.......you'll have an efficient and quiet marker, but your pump stroke wont be the lightest
easy way i do it is just to lower psi until it vents, then slowly increase psi until there is no venting. If this doesn't work you need to change springs, what i notice is that the worst venting and farting guns have too light a valve spring, and the worst farting by a stem that is too small for the valve body
to really know that your gun is not farting venting and efficient is to listen to it. it should have a tight pop or bang when your not using paint, and a very quiet pop when you are using paint....how quiet...like a quiet phantom
the best snipers i have heard sound like this, my first sniper2 was like that when i received it from Brad Nestle, it ran yellow springs and was quieter without a reg, yet still quiet with one.