Reg difference at different bottle pressure. Anyone experience it?

[ImpactX]

Anyone experience this. Say you set your reg pressure to 140 bar. When the bottle pressure is fill to 250 bar, the reg pressure will be 145 bar. Shoot a couple shot, bottle pressure now at 230-240 bar, reg pressure will be about 143 bar. When bottle pressure gets to 200 bar, reg pressure will be about 140 bar. And keep shooting, bottle pressure now 150 bar, reg pressure will be like 137 bar. I thought the point of the reg is to keep pressure behind the valve to the set pressure until bottle pressure falls below reg pressure. So shouldnt the reg pressure be 140 bar, even when bottle is 250 down to 140 bar?

 

[rsfrid]

Especially in guns such as the Avenger, when you fill tank above twice the reg setting, poi changes. This may be true with bottle guns as well. Just to be sure, I try to keep fills at about twice the main reg pressure setting. For 1800psi reg setting I fill to no more than 3600psi. This help control fliers and poi shifts. There have been studies done on this and demonstrated on youtube. Not quite on topic, but probably has to do with changes you see.

 

[rcs9250]

My air gun mechanics isn’t advanced enough yet to know but I do remember from my early gas welding days that single stage regulators were prone to that (same in scuba too). Single stage keeps the price down but not without side effects. When they came up with two stage regulators it really smoothed that out. I don’t know if airguns are single or two stage.

 

[nervoustrig]

The effect is analogous to line regulation of a power supply...how much its output changes based on the input. Some regulators do a better job than others.

Also potentially at play here is the surface quality of the regulator’s valve seat. A worn surface or one with scratches or machining marks will not settle to a stable pressure as well.

 

[Motorhead]

Yup ... results from the design of a regulators seat, both in size and how the HPA is exposed to the HP end of spool. ( center intake or side )

 

[rcs9250]

ImpactX, curious if others with your same model experience the same symptom. The gages on any airguns I’ve seen are by no means impressive, even the digital ones. Maybe your gage is inaccurate.
During the pressure readings you have observed have you by chance had them on a chronograph to see if there’s a velocity drop ? If velocity variance is minimal (like you typically see in review videos like AEAC’s or AoA) then I would say it’s a gage issue. Obviously vertical stringing in shot groups would be indicative of lower velocity from lower pressure.
Randy

 

[Scotaty]

The larger the plenum size the larger the effect you see.

 

[bigHUN]

For this same reason I decided investing into a tether setup. This Huma externally adjustable Reg takes care of the business as a pre-Reg. I pre-set it at 185 bars (but it is adjustable to your liking) and the Impact Reg is at 141 bar or whatever needs to be.

 

[ImpactX]

ImpactX, curious if others with your same model experience the same symptom. The gages on any airguns I’ve seen are by no means impressive, even the digital ones. Maybe your gage is inaccurate.
During the pressure readings you have observed have you by chance had them on a chronograph to see if there’s a velocity drop ? If velocity variance is minimal (like you typically see in review videos like AEAC’s or AoA) then I would say it’s a gage issue. Obviously vertical stringing in shot groups would be indicative of lower velocity from lower pressure.
Randy

I'm using wika 28mm gauges from huma and tested with my tanks larger gauge and it is same. I also switch the gauge from the front to the reg side and it still does it. Tested over chrony and I do see a fps difference of 30-40 fps. So it isn't just inaccurate gauge. The reg pressure does increase/decrease. Sort of like reg creep, but it does hold reg pressure over night if bottle pressure doesn't change. It only happens when the bottle pressure is higher to a certain point that you see the reg pressure changes.

 

[rcs9250]

What model rifle is it ?

 

[nervoustrig]

Tested over chrony and I do see a fps difference of 30-40 fps.

A variance of 8 bar around a 140 bar nominal setpoint represents a difference of less than 6%. If you adjust the hammer spring tension to the velocity knee (95-97% of max velocity), the 30-40fps swings will evaporate.

 

[bigHUN]

Have you ever filled with air and moisture inside? The Reg can look nasty. I don't really remember why I toke it apart maybe just a regular maintenance and cleanup, but after I saw this I bought a biggest moisture separator I could find on aliexpress.

 

[douger]

yeah thats terrible dirty reg that sure would affect it i would think

 

[Airgunmann]

Change it to brass piston could also help if it's the amp reg it would fit

 

[bigHUN]

ppl, don't just buy always new .... fix it ! Spend that $ for lead and range time.

 

[Vetmx]

Come on bigHUN, that’s how most PCP guys try to fix things. Spend more money on stuff. ImpactX, follow what Nervoustrig said in post 11. You never mentioned how you tune your gun but if you are running an internet full blast tune with your hammer spring, then your shots are definitely going to follow the bottle pressure. I’m not sure how long you had the gun or how much time you spent playing with the reg so there is a possibility that a new piston may help tighten things up a little. The reg on my RTI swings a little from fill to refill and even though I have my hammer set where it should be, I can see by my velocities climb when I approach 200b. The gun goes from 914-919fps to floating around in the 920’s. But my targets tell the only tale I’m truly interested in. All the pellets land where they should so who cares about the numbers.