Helpful tuning tips and links

[oldpro]

 Your not helping...

[Motorhead]

Your not helping...

Lol .... but I could 

When a set up has velocity INCREASE as pressure within tank is DECREASING .... tells you a few things are in play 

One being valves poppet is rejecting the opening force exerted by the hammer.
Could be Too Light of a hammer. Too light a hammer spring, TOO HEAVY a poppet spring, Too short of stroke along with a few other reasons. 

When one understands the PRESSURE within a given valve on it's own is holding the poppet shut and must be overcome to get valve to lift and flow some air ... understanding this small piece of the puzzle much more comes into focus 

As you were TEACHER 

[oldpro]

 Scott of course is correct and For the less informed heres the fix(normally) You can do one or two things normally but may require both. First increase hammer strike so there is more energy to open said valve at that pressure OR lower fill pressure so less hammer energy is needed to open valve or a combo of both.

[Tater]

Great thread! I appreciate the easy-to-understand-for-noobs explanations of the adjustments.

[Dairyboy]

Thanks for this. Love the sites to figure out efficiency and hopefully can tune my guns even alittle better from all this info.

[Verminstalker]

Ok if you were paying attention than you should be able to tell whats wrong with this tune. ANYBODY dont be shy its a learning experience.
Created: 10/16/14 11:04 AM
Description: WAR carbine
Notes 1: low speed tune HT 7 HS 0
Notes 2: 2900psi to 2400
Distance to Chrono(FT): 1.00
Ballistic Coefficient: 1.000
Bullet Weight(gr): 0.00
Temp: 62 °F
BP: 30.05 inHg
#          FPS  FT-LBS      PF
26    761      0.00    0.00   
25    764      0.00    0.00   
24    765      0.00    0.00   
23    757      0.00    0.00   
22    742      0.00    0.00   
21    742      0.00    0.00   
20    739      0.00    0.00   
19    727      0.00    0.00   
18    723      0.00    0.00   
17    716      0.00    0.00   
16    706      0.00    0.00   
15    704      0.00    0.00   
14    700      0.00    0.00   
13    697      0.00    0.00   
12    696      0.00    0.00   
11    691      0.00    0.00   
10    684      0.00    0.00   
9    676      0.00    0.00   
8    671      0.00    0.00   
7    665      0.00    0.00   
6    666      0.00    0.00   
5    661      0.00    0.00   
4    654      0.00    0.00   
3    646      0.00    0.00   
2    643      0.00    0.00   
1    636      0.00    0.00   
Average: 701.2 FPS
SD: 40.0 FPS
Min: 636 FPS
Max: 765 FPS
Spread: 129 FPS
Shot/sec: 0.1
True MV: 701 FPS
Group Size (in): 0.00


Sent from my iPhone

Valve not able to overcome pressure till late in the string. More preload on hammer spring?

[oldpro]

 Exactly you need more preload and possibly a lower fill pressure to boot. Good job! Ill throw some stumpers on in a bit.

[aceflier]

I could have used this a week ago. Oh well learned the long and painful hand pumping way. Still watching in case I need to try something. I can't leave well enough alone sometimes.

[int3man]

Also remember that when running your string dry fire the first round always its a waste shot that will only screw up your string or misguide you Ill explain why later.

O.K.  Obi-Wan Kenobi  Luke here, please explain the Jedi Mind Trick, "wasted first shot" as promised. 

From what I can tell the PE is the same and the Friction is the same so the KE should be the same.  The only thing that has changed since your last shot was the fill pressure and it has come back to where you first started.  So why is it a wasted shot???  Is it the Dark side of the Force?

I have seen it always lower but I have no clue as to why.

Thank you.   Obi-Wan

Michael :- )

[Dsrieth]

I was looking at your suggested parts to get and noticed that the audio cable that you listed only has two rings, whereas my Caldwell ballistics chrono cable has three rings. I tried using a two ring cable and it wouldn't make connection. Did u end up using a 2 ring connector cable on yours, or is the one in your link suppose to be a 3 ring?

[int3man]

Hi it should be a 3 ring Data cable.  Same ones that you use for an I Pod. 

[oldpro]

Im sorry its this one I will go back and change it   

[MicErs]

Butthead LOL

What .... you saying string is ascending in velocity, what was I thinking !!!

You need a regulator !! ... still 

Yes, a regulator would give you more shots at a consistent velocity.  My BSA was doing the same thing.  I managed to get 70 shots out of it when I regulated it to 18 FPE.  Right now it is at 25 and I get 50 shots... but really I should tear it down and set it back to 18 FPE.

[oldpro]

   I get this question a lot. Why does my gun shoot slow when I fill higher than xxxPSI? Or why does my ES get huge when I over fill? Well its quite simple really there is a small valve head inside your gun that has pressure pushing it closed and its opened by the hammer when it hits the valve stem. So to open a valve at low pressure requires little hammer energy or how fast the hammer can travel to put it simply. So when you fill to high pressures there is way more pressure in the air tank pushing down on the valve head and requires more hammer energy to open it. Well that sounds ok BUT when you apply enough hammer energy to open the valve at high pressure it then opens the valve a lot at low power where it requires less hammer energy.  So most people will have a high pressure tune for higher power shots and a lower fill pressure tune for more consistent shots and a longer shot count.

[oldpro]

 MY gun get louder at low pressures??? Well once again this is all about potential energy and valve dwell so let me explain. There is vast more energy at 3K fill then at 2K fill so to push a given pellet to lets say 900FPS at 3k it takes very little dwell or how far the valve opens to get the pellet to speed where as at 2K fill the same speed requires the valve to be held open longer to use more air at a lower PSI to get the pellet to speed this is a long dwell. Long dwell shots waste more air and have the valve open longer thus more report from the barrel. So long dwell low pressure equals loud report and high pressure short dwell low report more of a snap where as a low fill long dwell is more of a woosh.

[Rocker1]

Good stuff Travis now I know everything almost sometimes what day is it?? seriously good stuff and thanks for shareing and the lesson. David

[Tims229]

MY gun get louder at low pressures??? Well once again this is all about potential energy and valve dwell so let me explain. There is vast more energy at 3K fill then at 2K fill so to push a given pellet to lets say 900FPS at 3k it takes very little dwell or how far the valve opens to get the pellet to speed where as at 2K fill the same speed requires the valve to be held open longer to use more air at a lower PSI to get the pellet to speed this is a long dwell. Long dwell shots waste more air and have the valve open longer thus more report from the barrel. So long dwell low pressure equals loud report and high pressure short dwell low report more of a snap where as a low fill long dwell is more of a woosh.

I've noticed this when my jkhan bullpup goes off the regulator. I can literally hear when I'm off the regulator because the report sound changes. There is also more of a spring twangy sound after off the regulator. Probably because at that point, I have more hammer energy than needed to open the valve.

[oldpro]

 Your right on the money Tim. The valve is being held shut at a constant pressure with the Reg. and when it drops below the Reg. set pressure than you have over dwell = opening the valve to far and to long.

[GLPalinkas]

Also remember that when running your string dry fire the first round always its a waste shot that will only screw up your string or misguide you Ill explain why later.

O.K.  Obi-Wan Kenobi  Luke here, please explain the Jedi Mind Trick, "wasted first shot" as promised. 

I agree, Come on Travis.... You are still teasing us. Inquiring Minds want to know.. LOL

THANK YOU for this thread. Very educational.

[oldpro]

 When using loyds PCP Air Efficiency Calculator  http://www.calc.sikes.us/1/index.php  You need to know your tank volume this can be found here for the most common PCPs http://www.airgunsofarizona.com/Tanks/GunVolumes.html