Tuning Increase in fps when dropping off regulator…

[EPG]

I’ve got a HW110 .22 that I’ve tuned down.

It was originally “FAC” - about 29 ft/lbs with JSB 18.13g.

I dropped regulator pressure to 112 bar and replaced hammer spring shuttle with lighter UK spec shuttle.

I’m now getting well over 100 shots on a fill at 680-700 fps with 14.3g.

However, it seems to jump up about 20 fps when “falling” off the regulator.

I previously set regulator to 105 bar - and had same type of jump.

To get rifle to gradually drop velocity when falling off regulator, what adjustment(s) should I do?

-Ed

 

[wildcj5]

I’ve got a HW110 .22 that I’ve tuned down.

It was originally “FAC” - about 29 ft/lbs with JSB 18.13g.

I dropped regulator pressure to 112 bar and replaced hammer spring shuttle with lighter UK spec shuttle.

I’m now getting well over 100 shots on a fill at 680-700 fps with 14.3g.

However, it seems to jump up about 20 fps when “falling” off the regulator.

I previously set regulator to 105 bar - and had same type of jump.

To get rifle to gradually drop velocity when falling off regulator, what adjustment(s) should I do?

-Ed

I might be talking out of turn here but I think they set the reg at 85-90 bar on the 12ftlb guns.

Check out his vids I think he covers it.

 

[cavedweller]

I’ve got a HW110 .22 that I’ve tuned down.

It was originally “FAC” - about 29 ft/lbs with JSB 18.13g.

I dropped regulator pressure to 112 bar and replaced hammer spring shuttle with lighter UK spec shuttle.

I’m now getting well over 100 shots on a fill at 680-700 fps with 14.3g.

However, it seems to jump up about 20 fps when “falling” off the regulator.

I previously set regulator to 105 bar - and had same type of jump.

To get rifle to gradually drop velocity when falling off regulator, what adjustment(s) should I do?

-Ed

following!

 

[nobody1]

The effect of the velocity raising when the air pressure dropos below the regulator setpoint is described here:

Tuning Regulated PCP Airguns - Hard Air Magazine

The first thing you need to understand when tuning regulated PCP airguns is that for any PCP there is a maximum velocity for a given pellet,

hardairmagazine.com

"
Conversely, if you are tuned on the downslope (10% or more below the plateau velocity – the grey curve), as the bottle pressure falls, and the output pressure creeps downwards, the velocity increases slightly.

Then when you hit the setpoint, and the regulator stops regulating, the output pressure starts to drop more rapidly. Then the velocity INCREASES, developing a bell-curve, just like an unregulated PCP. (Because below the setpoint, it is unregulated).
"

 

[EPG]

The effect of the velocity raising when the air pressure dropos below the regulator setpoint is described here:

Tuning Regulated PCP Airguns - Hard Air Magazine

The first thing you need to understand when tuning regulated PCP airguns is that for any PCP there is a maximum velocity for a given pellet,

hardairmagazine.com

"
Conversely, if you are tuned on the downslope (10% or more below the plateau velocity – the grey curve), as the bottle pressure falls, and the output pressure creeps downwards, the velocity increases slightly.

Then when you hit the setpoint, and the regulator stops regulating, the output pressure starts to drop more rapidly. Then the velocity INCREASES, developing a bell-curve, just like an unregulated PCP. (Because below the setpoint, it is unregulated).
"

Thanks for the link to the article, exactly the info I was seeking.

 

[EPG]

The effect of the velocity raising when the air pressure dropos below the regulator setpoint is described here:

Tuning Regulated PCP Airguns - Hard Air Magazine

The first thing you need to understand when tuning regulated PCP airguns is that for any PCP there is a maximum velocity for a given pellet,

hardairmagazine.com

"
Conversely, if you are tuned on the downslope (10% or more below the plateau velocity – the grey curve), as the bottle pressure falls, and the output pressure creeps downwards, the velocity increases slightly.

Then when you hit the setpoint, and the regulator stops regulating, the output pressure starts to drop more rapidly. Then the velocity INCREASES, developing a bell-curve, just like an unregulated PCP. (Because below the setpoint, it is unregulated).
"

So with my current tune, it seems that I’m somewhere between the gray and yellow line - as I’m getting a modest velocity increase of just 20fps as my rifle hits the regulator pressure .

If I’m understanding the article correctly, to get closer to the yellow line tune, I either need to (1) increase hammer spring preload or (2) decrease regulator pressure.

Is my understanding correct?

 

[ctshooter]

I had to read the article to provide some help here (really good article btw and explains it all very clearly).

I would say you are closer to the grey line than the yellow right now.

The approach I would take is to slowly increase your hammer spring and test fps each time until you reach max velocity. Then you would come back down -5% for peak efficiency. This will give you an idea of how high the regulator is set (in relation to max fps) and give an idea how much you want to reduce the regulator setting to get you target fps to be equal to max fps -5%.

 

[Headshots]

So with my current tune, it seems that I’m somewhere between the gray and yellow line - as I’m getting a modest velocity increase of just 20fps as my rifle hits the regulator pressure .

If I’m understanding the article correctly, to get closer to the yellow line tune, I either need to (1) increase hammer spring preload or (2) decrease regulator pressure.

Is my understanding correct?

Sounds right to me.

Find the peak like CT shooter is saying then back off some.

 

[EPG]

Sounds right to me.

Find the peak like CT shooter is saying then back off some.

Yep.

I may max out available hammer spring preload before I hit peak - in which case I will have to decrease regulator pressure.

 

[Headshots]

Yep.

I may max out available hammer spring preload before I hit peak - in which case I will have to decrease regulator pressure.

When I get close to max preload I stop and take the mag out the turn the HS to max preload until it wont engage the sear , or reset the trigger, and count the revolutions so I stay short of where it won't cock. I had a double feed because of it. This is on a FX Mav.

And yes lowering the reg pressure will work . Or for some ,wanting more power, it's time for a heavier hammer or stiffer HS.