Tuning Tuning - Shot Count vs Reg Pressure

[Bogview]

When tuning for a specific velocity, does the shot count increase with lower reg pressure and increased hammer spring pressure?

 

[TMH]

To a point, generally yes.

But if you go too low on the reg you might really have to be banging that valve open with a high hammer spring tension. This can lead to some lower overall air use efficiency.

Then upping the reg just a bit and backing off the HS just a bit might get you better efficiency and higher shot count.

Its all a balancing act.

 

[Drumsnguns]

If you increase the hammer spring w low reg pressure you risk over powering the valve and keeping it open too long. This will waste air and your shop count will indeed drop. 


what works for me is:

1. max out the HSTA on MAX power wheel. 
2. Increase the reg pressure til you go about 10 FPS over the speed you want. 
3. Decrease the HSTA to the point where you see the velocity START to drop. 


Then find the power wheel setting to give best groups at say 60 yards. That’s your tune. Mine likes C on the PW. 
Measure the HSTA position w calipers record that then loc-tite it. 


Next, turn your valve knob in, ( start the process with it all the way out at 4 lines), a little at a time while shooting over the chrono until again you START to see the speed drop. 

This should give you the most efficient tune.

 

[stoti]

Generally, a short, high pressure burst of air is more efficient than a long, slow, poof of lower pressure air.

Stoti

Here is more detailed info from the master...Great information!

https://airgunguild.com/ask-bob/tuning-a-regulated-pcp/

 

[Parrotculler]

And don't forget to ensure that the ports are 80% of the caliber all the way thru, and that the plenum size is adequate.That's often the ticket to a low reg set point plus a mild HST avoiding hammer bounce, yet decent power. If you still experience air wastage "after elvis has left the building" you may need to lighten the hammer and/or work on your hammer spring (dual springs or SSG, see the separate forum thread on those little miracles).

I was able to get amazing efficiency and accuracy with my regulated PR900w by achieving a good balance.

It's the entire system ...

 

[Bogview]

I'm not sure there is a right answer. There are allot of variables involved that can't be accurately measured where the magic happens.

 

[qball]

Generally, a short, high pressure burst of air is more efficient than a long, slow, poof of lower pressure air.

Stoti

Here is more detailed info from the master...Great information!

https://airgunguild.com/ask-bob/tuning-a-regulated-pcp/

100% and especially true with shorter barrels! 


best power and efficiency is achieved when the valve closes just before the pellet or slug exits the barrel. Longer the barrel the lower the reg pressure is required to accelerate the projectile up to the desired speed. At the end of the day the amount of air needed for accelerate a projectile of given mass is about the same as long as the valve closes in time not to waste air. 


so the answer is lowest reg setting to shoot the projectile at desired speed with the valve closes right before the projectile exits the barrel. How to do that? Just listen to your gun according to the airgun legend Ted bier. 

https://youtu.be/VjqD-eQwyHo




To put things into car terms if we need to get a 3000lb car to 60 mph in 1/4 miles then you just need to hit the gas pellet a little and take your time to 60mph. If you shrink that down to 100 yards then you might need to floor it but the amount of time the engine runs will be a lot shorter. 

 

[Bogview]

This is allot like powder burners, If you see flame coming out the end of the barrel, it indicates that there is too much powder that is burning too slow. The solution is hotter powder and a hotter primer. With an airgun this would be similar to too low of a reg pressure and too much valve opening resulting in wasted air.