Air Venturi Aveger loss of power

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S

stroke

Member
Dec 21, 2023
16
3
St. Louis 63136
Tying to I.D. a loss of power in both a .177 and .22 Avenger.

Both a .177 & .22 operated correctly for 6-9 months, then the loss of power in both guns. Spent 4 months sending the .177 back to Air Venturi multiple times. No joy!

I first measure efficiency with a chrono. I measure mutiple reg pressures looking for the knee. Enjoyed shooting well for 6-9 months. Now I get a 80-100 fps drop in efficiency compared to the original numbers. Also shooting, used to get 2nd zero at 60 yards, now its 45 yards (backyard max range).

Didn't notice any air leaks. Cleaned the barrel. Virgin at taking the gun apart, but I got the Aveger seal kit and replaced the reg and hammer spring. Didn't fix the problem. I read on posts the O rings need lube or replacing under the reg.

How do you get the Belleville washers and O rings out for servicing. Looks like you need to force them. Didn't want to without more info.

Replaced the reg with no service to the O rings because I didn't know to remove them.
 
WorriedMan said:
Two guns, experiencing the same symptoms at approximately the same time would have me searching for what they share in common, starting with the air delivery system. Are proper moisture control systems in place? WM
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Different times, .177 6 months ago, the .22 the end October. Using a gxPump cs2. Proper controls in place. Good though though. Don't think its the reg O rings?
 
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Did the pressure indicated on the 2nd gauge change between then and now? If not, you can set aside the regulator as the cause of the power loss.

Davee1’s point about the bolt O-rings is a good thing to check. Usually a failing O-ring there will cause several symptoms...loss of velocity, wild velocity swings from shot to shot, and a loud pop on firing.

You described having taken it apart and even replacing the hammer spring. How did you adjust the hammer spring tension after you got it back together?
 
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nervoustrig said:
Did the pressure indicated on the 2nd gauge change between then and now? If not, you can set aside the regulator as the cause of the power loss.

Davee1’s point about the bolt O-rings is a good thing to check. Usually a failing O-ring there will cause several symptoms...loss of velocity, wild velocity swings from shot to shot, and a loud pop on firing.

You described having taken it apart and even replacing the hammer spring. How did you adjust the hammer spring tension after you got it back together?
Click to expand...
Shooting today, have to wait til temp is > 40F in St.Louis or I'm too cold. Army gave me a gift of a blizzard and ice storm. I have the Chony set up in my basement. I'm unclear, made the reg and hammer spring mods on the .22 so far. Did Replace the bold O-rings on the .22 and silicon oiled. Shot efficiency in the basement, numbers were down compare to original when shooting well in the past. Then I did the O-ring delete kit when I got the tubing. Shot last week in the backyard. Numbers were down compared to original (45 yards second zero compared to 60 yards). Delate kit did result tighter shot placement.

Reg pressure sounds like what I've read in other posts. Set point increases from initial to 200 fps over 5 minutes, reg pressure never reaches fill pressure.

Hammer spring same setting as in original settings? Hammer spring has same turns 0 - 5.87 turns.
Going to shoot in the backyard now. Will replay with update.
 
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In the original post you said you replaced both the regulator and the hammer spring. This question is important so I will ask again, is the regulator currently set to the same pressure as before? If so, then the only thing left to do is to dial in the hammer spring tension until you find the velocity plateau, and then back it off to the velocity knee (approx. 97% of the plateau)

If the result is 80 – 100fps less than what it was doing before, it means something is affecting the delivery of air after the hammer knocks the valve open. One potential cause is a failing bolt O-ring like was brought up earlier. Another example would be the barrel port is misaligned to the valve’s exhaust port, causing the airflow to be restricted.
 
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stroke said:
Shooting today, have to wait til temp is > 40F in St.Louis or I'm too cold. Army gave me a gift of a blizzard and ice storm. I have the Chony set up in my basement. I'm unclear, made the reg and hammer spring mods on the .22 so far. Did Replace the bold O-rings on the .22 and silicon oiled. Shot efficiency in the basement, numbers were down compare to original when shooting well in the past. Then I did the O-ring delete kit when I got the tubing. Shot last week in the backyard. Numbers were down compared to original (45 yards second zero compared to 60 yards). Delate kit did result tighter shot placement.

Reg pressure sounds like what I've read in other posts. Set point increases from initial to 200 fps over 5 minutes, reg pressure never reaches fill pressure.

Hammer spring same setting as in original settings? Hammer spring has same turns 0 - 5.87 turns.
Going to shoot in the backyard now. Will replay with update.
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Don't know if you can read exel files but if you can. Otherwise I'll try some thing else before I send backyard shooting data.

Hopefully I answered the bolt probe question. Like to know more about the "barrel port is misaligned to the valve’s exhaust port". Stroke affected speech & writing. Took me an hour to write the 2:18pm message above.

View attachment 2500 reg Ham.xls
 
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stroke said:
Like to know more about the "barrel port is misaligned to the valve’s exhaust port".
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No problem, here's a diagram with these two features in bold red text.

PCP valve markup.gif


A few potential reasons why they may not be aligned:
  1. the barrel was not fully inserted into the receiver before the grub screws were snugged up
  2. the barrel was rotated slightly before the grub screws were snugged up
  3. these features are inherently misaligned because of manufacturing tolerances or error
 
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nervoustrig said:
No problem, here's a diagram with these two features in bold red text.

View attachment 421603

A few potential reasons why they may not be aligned:
  1. the barrel was not fully inserted into the receiver before the grub screws were snugged up
  2. the barrel was rotated slightly before the grub screws were snugged up
  3. these features are inherently misaligned because of manufacturing tolerances or error
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per diagram Is the valve spring the O-rings/bellevilles under the reg. Only reason I ask I couldn't lube them as I couldn't remove the belleville washers when I replaced the reg.

Did you read the exel files. If so I'll send back yard shooting data tomorrow. Speech class tomorrow.
 
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stroke said:
per diagram Is the valve spring the O-rings/bellevilles under the reg.
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My diagram does not depict anything associated with a regulator, its Belleville washers, its O-rings, etc.

stroke said:
Did you read the exel files.
Click to expand...

Yes, a screenshot for the benefit of other readers:

image_2024-01-02_223910970.png


The above indicates a 2500psi regulator setpoint previously gave a plateau velocity of almost 980fps, whereas now the same 2500psi setpoint is only producing 920fps. With that in mind, I maintain that you want to be thinking about air delivery to the pellet...again, a couple of possible causes being blow-by due to a failing bolt O-ring, or misaligned porting restricting air delivery to the pellet.

Meanwhile there are a number of other possibilities if something we think we know is incorrect. For example, if the gauge has drifted or its label rotated and therefore 2500psi isn't really 2500psi. Or the two plateau velocities were recorded using different pellets. Or the chronograph readings contain some source of error, though it does seem likely that the velocity is down based on the diminished trajectory you described. I'm just trying to throw some things out for consideration.
 
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nervoustrig A hint or logic? If I remove the barrel, and check/replace ps-011-x-00 O-rings (H in Captain O-rings kit), does this correspond to "barrel port" in the diagram you sent? If so I'll do that.​


I bought a second reg kit to replace in my .177. I'd like to check the O-rings under the reg. Please I have asked before, how do you get the belleville washers out so you can check the O-rings. I ask because in previous posts it sounds important. Don't want to force them out (unless necessary), & do damage. I'm a newbie.
 
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