Q&A with the Air Venturi Avenger Product Manager, Tyler Patner

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In the Avenger Bullpup tuning guide, Steve says that he couldn't get the power any lower because the hammer spring is too stiff.



He also says that if your hammer spring is too high and reg too low you will have a descending shot curve.



Can you elaborate on the physics of this?



I can't seem to wrap my head around it.



My .22 Avenger has a descending shot curve when I have the hammer spring all the way out and the reg set to 1400 to shoot 16 gr pellets, so I know that it does happen, I just can't understand why.



I wouldn't think that it would matter with a regulated gun. 



Thanks



Andrew
 
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In the Avenger Bullpup tuning guide, Steve says that he couldn't get the power any lower because the hammer spring is too stiff.

He also says that if your hammer spring is too high and reg too low you will have a descending shot curve.

Can you elaborate on the physics of this?
Click to expand...

It is a result of the real-world characteristics of a regulator being imperfect. A regulator’s output pressure goes up and down with the reservoir.

Most everyone seems to report better results with the Avenger by not filling to the maximum pressure, suggesting the regulator’s pressure goes up along with the reservoir by a fair amount. Some pressure variation is okay when the hammer spring tension is adjusted optimally. That is, it will behave like a conventional PCP that is operating near the top of its bell curve…the pressure can vary up and down but the velocity remains stable. It’s usually referred to as tuning to the knee (95 – 97% of peak velocity), or called a balanced state of tune, or the hammer spring and regulator are adjusted in harmony.

However if the hammer spring tension is adjusted too high, you will get a descending string. Why is that? When the pressure is high, the valve is harder to knock open (more pressure holding it closed) but because there is an excess of hammer strike, the valve is still knocked open forcefully and you’re getting every ounce of push it can muster. And then as the pressure tapers down, the valve is even easier to knock open so it continues to give you everything it’s got but less pressure means less velocity. Thus a descending string.

The reverse is also true. If the hammer spring tension is adjusted weakly, the hammer can barely knock open the valve so the velocity is low. Then as the pressure falls, the hammer can knock open the valve more completely and the velocity begins to rise, i.e. an ascending string. And then of course if you kept going, eventually the pressure will fall so low that the velocity will again begin to fall.

I hope this helps lift the clouds a little.
 
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In the Avenger Bullpup tuning guide, Steve says that he couldn't get the power any lower because the hammer spring is too stiff.

He also says that if your hammer spring is too high and reg too low you will have a descending shot curve.

Can you elaborate on the physics of this?
Click to expand...

It is a result of the real-world characteristics of a regulator being imperfect. A regulator’s output pressure goes up and down with the reservoir.

Most everyone seems to report better results with the Avenger by not filling to the maximum pressure, suggesting the regulator’s pressure goes up along with the reservoir by a fair amount. Some pressure variation is okay when the hammer spring tension is adjusted optimally. That is, it will behave like a conventional PCP that is operating near the top of its bell curve…the pressure can vary up and down but the velocity remains stable. It’s usually referred to as tuning to the knee (95 – 97% of peak velocity), or called a balanced state of tune, or the hammer spring and regulator are adjusted in harmony.

However if the hammer spring tension is adjusted too high, you will get a descending string. Why is that? When the pressure is high, the valve is harder to knock open (more pressure holding it closed) but because there is an excess of hammer strike, the valve is still knocked open forcefully and you’re getting every ounce of push it can muster. And then as the pressure tapers down, the valve is even easier to knock open so it continues to give you everything it’s got but less pressure means less velocity. Thus a descending string.

The reverse is also true. If the hammer spring tension is adjusted weakly, the hammer can barely knock open the valve so the velocity is low. Then as the pressure falls, the hammer can knock open the valve more completely and the velocity begins to rise, i.e. an ascending string. And then of course if you kept going, eventually the pressure will fall so low that the velocity will again begin to fall.

I hope this helps lift the clouds a little.
Click to expand...

Thanks!



That is kind of what I figured,.but wanted some clarification. 



Basically the regulator in the Avenger( or at least my Avenger)is less than stellar.



I do notice much tighter extreme spreads when I only fill it to 3000-3500psi.


 
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Parts availability has been brought up, but I think that's a big one.

I would like to add an opinion to it. I would like to continue to see a good functioning avenger at this price point ($350), but also upgradable. I realize this is the dream for probably every product ever made. After replacing one of the air reservoir o-rings with low miles on it, I was VERY tempted to make it a bottle gun not only for performance, but to reduce the number of o-rings required to hold a charge of air.
 
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A properly functioning PCP should lose no perceptible amount of air. Keep it charged with air as long as you are using it on a routine basis. If you plan to store it for months, it is not unreasonable to take it down to a little under the regulator’s setpoint. Say, if the regulator is set to 2000psi, you might shoot it down to 1800psi before putting it away. Or just keep it fully charged.


Emptying it completely is not helpful because seals can sometimes relax and may have difficulty sealing when you go to air it back up.


 
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Should not leak air. Keep it charged when storing it. The only time you would discharge it is when you're working on it like replacing seals or when you want to lower the regulator pressure. The manual it comes with is pretty well written. 

This video will help you when tuning.

https://youtu.be/2D_Zml_2wd4



Enjoy your new airgun, it shoots well.
 
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I just put an F X Coronagraph on an Avenger with Rubber Bands it caused the Pellet to 

hit 1.5 inches low 

So I mounted it with Velcro problem for me was solved see Photos 



Larry ( New Member)
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Just purchased a .22 Avenger rifle. Tried slugs, but no go. Just not enough power to get the lightest slug over about 850 fps (FX Hybrids). tried 4 other slugs, all slower at maxed reg and maxed hammer spring. Curiously, the tuning guide said I should get 5.5 rotations on the hammer spring before it maxes out, but I only get 4, could there be something on the inside of the gun holding the hammer spring back?

many thanks up front.
 
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Just purchased a .22 Avenger rifle. Tried slugs, but no go. Just not enough power to get the lightest slug over about 850 fps (FX Hybrids). tried 4 other slugs, all slower at maxed reg and maxed hammer spring. Curiously, the tuning guide said I should get 5.5 rotations on the hammer spring before it maxes out, but I only get 4, could there be something on the inside of the gun holding the hammer spring back?

many thanks up front.
Click to expand...

I use the .22 Griffin pellet base 19gr slugs. 910 fps They work great out of my Avenger. Reach out and touch prairie dogs 120+ yards. Kinda pricy.



Edit: There's a rough spot when you are turning the hammer spring out. You have to kind of force it to get 5 turns out. I believe it was a mistake when he did that on his tuning guide. Mine only has 4 turns because I did not go past that rough spot. There's also 2 set screws on the left and right hand side that hold the hammer Spring adjustment from moving after you get it set you want to tighten those. If not, eventually you'll lose your tune from the hammer spring backing out.

Haven't seen anybody mention those set screws yet.
 
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