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Author Topic: Sniper/Cocker Pump Tuning and Farting Guide  (Read 21808 times)
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Koa
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« on: October 11, 2008, 07:37:28 PM »

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.
« Last Edit: June 21, 2009, 06:26:32 AM by Koa » Logged

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« Reply #1 on: October 11, 2008, 07:38:08 PM »

Another post i did on farting....has different structure, but not as indepth as first post, but might help see a bigger picture and is for regulated setups only

farting can be helped by a few things

harder mainspring tension:
the a gun farts, the hammer bounces, if you increase the main spring strength then the hammer cant bounce back up as high or as much

lighter valve tension:
the valve spring will push the valve stem closed after a shot, the stiffer the spring the harder the bounce back will be, its almost like a rubber super ball from the candy machines,  when i do put in a red valve spring my gun would fart even worse, due to the valve spring bouncing the hammer more.

good valve springs are CCM valve, Maddman SEAR, FreeFlow lightest valve & sear, and my all time favorite spring is the Omega Roller trigger kit sear spring, its stiffer than the rest yet still very light compared to maddman green and stock.

lower psi:
almost like the valve spring, the psi behind the valve will push the valve stem closed after a shot, the higher the psi the harder the bounce back will be, its almost like a ball filled with air, the more air that is in the ball, 1. the harder the ball is = harder to open the valve, and 2. the more it will keep bouncing after dropped = just like the hammer

cup seal material is too hard:
the harder the matierial the less it will "stick" to the valve body, trust me on this i tested it......its amazing to me, the harder the cup seal the less flexing around the valve body there is, so there a smaller surface area sealing the valve, this is bad for rough surfaces but great for opening at high pressures. bad for us that this contributes to farting

Hammer face has indention, or valve stem too short
if your hammer has those indention lathed into it, your probably getting a tad more FPS, but then your getting a weaker spring strength where the hammer hits the valve, so when it hits the valve its easier for it to bounce, same for the valve stem. changing either one of these wont help that much.

problem is:
there is no set way to fix farting, but if you are smart, your get a spring kit and fiddle with your reg, if your lazy your pick up a new hammer or a ccm valve, old ones farted BAD, new ones mmmmmm mmmmmm good, i have made a very quiet smooth sniper with one of these valves.
« Last Edit: June 15, 2009, 12:46:54 AM by Koa » Logged

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« Reply #2 on: June 03, 2009, 08:41:39 PM »

If there are any question or if you need clarification post up
« Last Edit: October 27, 2009, 07:25:17 PM by Koa » Logged

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« Reply #3 on: November 07, 2009, 09:36:33 PM »

 Cheesy Yeah , they have no common sense and i can barely under stand what they are saying most of the time.
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« Reply #4 on: November 07, 2009, 09:38:46 PM »

then how come you still cant tune your gun and need me to do it when i provided all the information needed in this forum?
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« Reply #5 on: November 07, 2009, 09:40:23 PM »

Lets just say i have absolutely no time to do it and my parents dont like it when i fiddle around with my guns. When im at the field im reffing and cant really tune it.
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« Reply #6 on: November 07, 2009, 09:42:09 PM »

what...just cough when you pull the trigger!
COUGH*BANG, man this swine flu
COUGH*BANG uh anyone got a halls?
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« Reply #7 on: November 07, 2009, 09:45:37 PM »

Lol , I need a chrono to if im gonna do it at home. That swine flu is some serious stuff man my brother in Oregon has it , glad he doesnt live down here.

But yeah they get mad when i take apart my gun to clean and stuff.
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Koa
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« Reply #8 on: November 07, 2009, 09:52:42 PM »

no need chrono, just do by sound, then chrono the next day, should be 260 then you just go higher and higher with each until you get 300
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« Reply #9 on: November 07, 2009, 09:53:59 PM »

Mmmm , I wana try Green Valve Green Main and PSI - FPS.
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Koa
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« Reply #10 on: November 18, 2009, 01:27:44 AM »

those are too hard
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