Air Venturi Avenger Hand Pump Tune
Boy was I wrong! Having completed the Air Venturi Avenger Power Tune, I had low expectations for an Avenger Hand Pump Tune. That is a tune based on a fill pressure of just 3,000 PSI, about the maximum that most of us can manage using a HPA hand pump.
Given that this Avenger Hand Pump Tune uses a fill pressure that’s waaaaay down from the 4,350 PSI maximum fill pressure, my expectation was for few consistent shots, and rather anemic ones, at that. Wrong, wrong, wrong…
In fact, we have a tune that gives no less than 90 consistent shots. Using 14.66 Grain H&N Field Target Trophy pellets again, these gave an average Muzzle Velocity of 801.84 FPS. That’s a very respectable 20.93 Ft/Lbs of Muzzle Energy with an Extreme Spread of 28.50 FPS across the 90 shots.
And – as you’ll see below – this tune even gives 48 consistent shots at a fill pressure of just 2,000 PSI. I’m very happy with that as an Avenger Hand Pump Tune! So how did we get there?
Establish A New Baseline
As with our Avenger Power Tune, I started by establishing a baseline of performance to work from.
The basic assumption was that – in order to achieve a reasonable number of shots per 3,000 PSI fill – we would need to use a low regulator pressure setting.
Following the steps outlined in the Avenger’s User Instruction Manual, the first step was to degas the gun to empty it of pressure. I found that the air relief valve needed only about 1/8 of a turn with the Allen wrench. Once the hissing had stopped, the pressure gauges read zero and a dry fire produced just a click.
(BTW, a 3 mm Allen wrench required for this. It’s not the same as the one included with the gun which fits the hammer spring adjustment screw).
Next, I removed the cap that covers the regulator screw, then rotated it clockwise to the stop, then back a little.
After filling with 3,000 PSI of air, I rotated the regulator setscrew the tiniest amount counter-clockwise until the regulator pressure gauge read about 1,200 PSI.
The minimum regulator pressure specification for the Avenger is 1,160 PSI, so this “1,200 PSI” probably represents the lowest we can set, given our accuracy expectations for the gauge. So, we have somewhere around 1,800 PSI of usable air between the fill and regulator pressures.
Having set the regulator, it was time to run a series of baseline tests. For this, I took the 14.66 Grain H&N Field Target Trophy pellets again and fired a series of six, 10-shot strings across of the Chronograph at different hammer spring tension settings. The results were interesting!
It was clear that there was a significant increase in Muzzle Velocity when the hammer spring tension was increased by one turn. But going beyond three turns made no further practical increase, as we can see above. That 5.5 turns was the maximum rotation available, meaning that the factory setting of “about 3 turns” is about mid-way through the range…
So, it was clear to me that the hammer spring tension setting would have to be between one and three turns in. The Chrony had provided more information to help make that decision, however.
Practical experience of tuning regulated PCPs has convinced me that there is also much to be learned by paying attention to the Standard Deviation of these 10-shot baseline strings.
Generally a low Standard Deviation indicates that the gun is operating “in harmony” with that combination of regulator pressure, hammer spring tension and pellet weight. By “in harmony”, I mean good resulting shot count and FPS – probably not the highest of each, but a good overall balance.
The Standard Deviation figures were not bad at any hammer spring tension setting. However, it was clear that one turn in gave a result that was much superior to the others.
As my plan was to maximize the number of consistent shots at a reasonable power level for this tune, that’s why I decided to set the hammer spring tension one turn in.
But Wait – There’s Less…
Having amazed myself with the results of this tune, I decided to test the gun at exactly the same settings but with a fill pressure of just 2,000 PSI. That’s well under half the maximum fill pressure, of course.
As you can see below, the result was still 48 consistent shots. (Average Muzzle Velocity 796.6 FPS, 20.66 Ft/Lbs). Amazing! By calculation, that means these same settings would give us no less than 160 shots of around 21 Ft/Lbs with the regulator set to 1,200 PSI, were we to fill the Avenger to the full 4,350 PSI!!!
Clearly the Air Venturi Avenger can be set to provide a very strong shot count even at the relatively low fill pressures produced by a hand pump. It’s clear that I was completely wrong in expecting the Air Venturi Avenger to be unsuitable for use with a hand pump due to its high, 4,350 PSI, maximum fill pressure!
Yes, this Hand Pump Tune gives around 21 Ft/Lbs of Muzzle Energy, compared to the 36+ Ft/Lbs of the Full Power Tune. However, it’s still a decent power level and not too far from the 28+ Ft/Lbs of the factory tune. As a hand pump user, I’d be very happy with that.
Now I need to make one more tune. Let’s make that an Avenger Hand Pump POWER Tune!
Check back soon to see if we can increase the power without demolishing the shot count, yet still fill only to 3,000 PSI…
Here’s the other parts of this Air Venturi Avenger review: