Detuning the Avenger

[johnbrown]

My Avenger .22 with the minimum regulator setting of about 1200 PSI and 0 hammer spring turns gets about 850 FPS with CPHP.

Since I am only plinking I would like to lower the pellet velocity to around 700-750 FPS.
In theory that can be done by having lower regulator output pressure and a weaker hammer spring, but I already ran out of adjustment settings.

Has anybody detuned an Avenger even more and how did you do it?
Do you know any videos showing that?

[nervoustrigger]

You can either swap the Belleville washers with thinner ones to allow a lower setpoint, or restrict the flow somewhere between the valve and the pellet.

The former will yield a higher shot count than the latter. 

[Ribbonstone]

Think you are right...but the difference in air use isn’t as great as the shot count...but I had an odd point of view.

 Adjusting the reg down to  say 900psi vs strangling  the air flow at 1200psi….you get 300PSI of bonus air to use in a shot string.  Air use per shot  (efficiency) could be the same, but with 300psi more air to tap from, you get more shots per fill.

[nervoustrigger]

Efficiency favors high pressure.  That is, assuming a fixed power level that reasonably lies within the capabilities of the pressure range in question.  However like you said, shot count favors the additional working range.
 
I have to remind myself sometimes that efficiency by itself is a dead end goal.  Seeking to maximize it without due consideration to other factors will yield some pretty disappointing results.

[Ribbonstone]

Have to have some kind of arbitration. Some neutral party.... and what's more neutral than math?

Was tryng for 12 foot pounds for 200 shots from 215cc's (which you can take as a 13CUIN HPA bottle)

Easy was to use an 890psi reg output (ok was adverized at 850...tested it was 890)...and run it from 3K to 890psi.

More work was to use a 1200psi reg (that one tested at 1190psi) and fart around with spring tension streiker weights, anti bonce decices, transfer ports....but I got there.  Basically all that "extra" stuff to get to the same 200 shot goal for the same starting volume.

Pump filling, I did notice the difference between filling from 900-3000 vs filling from 1200-3000.

Compressor difference is a few seconds or run time....tank fill difference is less if the tank is full....pump fill difference is much more noticeable.

So it's more like a work-benefit-blance....in my case, I just pugged in a new bottle with a low output and got the goal of +200 shots and didn't have to mod the "guts".

I lost the math-arbitration.....guess I'm more results oriented than refinement oriented.

[johnbrown]

This is the only video I am aware of which shows how to disassemble the Avenger:


So the 2 main choices are:
1. Reduce regulator output pressure
There are few resources on how to do that in an Avenger.
The Avenger regulator (deeply buried in the receiver block) is hard to reach in order to tweak its Belleville washers for lower pressure.

2. Decrease hammer spring tension
The hammer spring seems to be easier to access than the regulator.
I do not want to cut the original hammer spring.
Anybody knows of a matching weaker spring?

[nervoustrigger]

Please note, dialing the velocity down by way of simply reducing the hammer strike will sacrifice consistency.  In other words, the extreme spread will go up.  What you’re doing is operating it at a state of partial valve lock…the valve doesn’t get knocked open consistently so the velocity ping-pongs all over the place.
 
Whether or not that is objectionable will depend on your particular shooting requirements, and of course where on the spectrum it lies between optimal hammer strike and complete valve lock.  However generally speaking, for anything other than short distance--say 20 yards or less--it’s probably not a good direction to go.
 
The other two options, reducing the regulator pressure and/or restricting the transfer port, do not suffer this shortcoming.

[johnbrown]

How would you restrict the transfer port for the Avenger PCP?

[avator]

Fill it with JB Weld and redrill it.

[nervoustrigger]

Yes, or see if you can get a piece of brass tubing the right size.  Cut off a little section of it and use red threadlocker to set it.

[johnbrown]

I found a way to detune the .22 Avenger to 680-700 FPS with 14.3 grain CPHP.

The Avenger manual (https://www.pyramydair.com/air-gunsresources/manuals/Air-Venturi-Avenger-air-rifle-manual.pdf) section which deals with adjusting the regulator states:
" Using a flathead screwdriver, rotate the adjustment screw clockwise until it stops
 (Fig. 9a), then rotate one quarter turn counter-clockwise (Fig. 9b). This will reset
 the regulator to a minimum setting."
After the one quarter turn I got a 1200-1400 PSI output pressure from the regulator.
I adjusted the regulator again but this time I did not do the one quarter turn, so the regulator adjustment screw was at zero (no turns).

These are the Avenger CPHP 14.3 grain velocities for different regulator output pressures (zero hammer spring turns):
800-1000 PSI, zero regulator screw turns, 680-700 FPS
1200-1400 PSI, one quarter counter-clockwise turn, 820-840 FPS
2400-2600 PSI (set from factory), don't know the number of turns, 950 FPS

[faelzimxds2]

Does anyone already have the dimensions of the sealing rings of the PCP Avenger .22? An Exploded View of the Carbine has the same Nova Liberty.

I would like to know which o-rings you have on it.