Hello anyone I'm looking for some help with my Avenger 22 caliber been having some problems with my point of impact change after refilling with air and I could really use some advice if anyone can help. I feel the reservoir to 3800 PSI and my regulator is set to 2100 PSI and I'm currently shooting jsb 15.89 pellets. At the top of my fill I'm averaging a 1 inch group at 45 yards and once I'm down to 3000 psi all the way down to 2100 PSI I can literally stack each pellet on top of each other and I'm wondering why the big difference
Tuning Poi change
- Thread starter Timothy8507
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MOST airguns I have experience with will have a slightly different POI if they're filled to their max. I only fill to the top of my gun's sweet spot & don't have a problem with shifting POI. My gun (FX Boss) can fill to 250 bar but it's sweet spot (where I get the most consistent string) is from 245 down to about 110 bar. If you're filling to max capacity try stopping your fill short of max & see if your POI is consistent. Accuracy, to me, is waaay more important than shot count so I never worry about not "being able" to fill to the max. I can't explain the technical aspect & reason for this but hope it helps with POI!
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How are you positioning your rifle when shooting? From a bipod or bags? Or shooting rest? Is your shroud clamp snug as it should be? Do you get blow-by from the probe O-rings? There are a lot of things to consider.
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2100 psi is pretty high for 15.89 pellets. I had mine at 1400 psi for 15.89 then went up to 1800 psi for 18 grain pellets. My ES runs about 5 (884 fps) and STD Dev 1.5. The speed and poi doesn't change from full fill (about 4000 psi) down to 1800psi. So I suggest looking for other areas such as leaks or variation in pellet weight or head size.
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At a full fill, you might be above the operation parameters of the reg, so check with the maker. If not, then it appears to not be working properly. I've noticed a bit of the same, although not to your extent. One of many things I can't explain.
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Make sure the air tube clears everything it does expand a little bit when filled and compress a tad when pressure is lowering some people have noticed the change with barrel bands and such and is a reason I like to keep a barrel more free floating as to say I don't know how your avenger is set up and others have a good point with sweet spots in rifles but the regulator is supposed to help out with velocity changes pellet weights as mentioned head size there are so many variables to consider
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This phenomenon will drive a guy nuts. With some guns it’s more obvious than others. Sometimes it’s so small that most pellet flingers might never notice it. Some projectiles show it more. I have used up some brain cells from time to time trying to work around it but never fully committed to a full scale investigation in order to be able to point my finger at the culprit. Once theorized that with a tube gun it was tube growth. But then you have a bottle gun do it and all that goes out the window. I currently try working around it when tuning a gun by making very very small HS adjustments. As to the guy with the Avenger having an issue, I think his might be easy to solve. His reg is set too high and he has an ever descending shot string.
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Thank you all for the information as this site has helped me numerous times in the past I appreciate the feedback. For me The Sweet Spot is roughly 3,000 PSI down to roughly 2,000 PSI which produces about 30 shots within a quarter inch at 45 yd. I originally started with a regulator setting of 1400 PSI and worked my way up to 2100 PSI with the same result being the last half of the shot string being the most accurate. If I could just figure out what's causing the in accuracy on the top half of the shot string this would be a phenomenal gun for me but it drives me crazy that I can get roughly three quarter inch groups and quarter inch groups within the same shot string again last half probably 30 shots being the most accurate at a quarter inch basically 1 pellet on top of the other. My issue is very consistent as I shoot from a bipod and bags under the butt of my stock. I feel like I can eliminate the type of pellet and my trigger pull as I have tried this maybe 30 times with same result
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Unfortunately I do not have a chronograph yet but with the issues I'm having I thought it'd be worth purchasing one to test my shot strings I have one on the way from Amazon and will be able to update just as soon as I can get out and test again I really appreciate any and all information thanks so much
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How in the world are you tuning a gun without a chronograph? I know pellets aren’t that expensive but holy smokes. While you wait for your antidote to arrive, read up on how to find the proper reg setting for your desired speed. No need to start a new topic, there is plenty out there to read. Some make it overly complicated. If it seems complicated, keep searching. One of us has posted how to do it in no more than five sentences.
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I have no experience with this rifle, and I can't say with similar confidence that it's a barrel band issue. In fact, I doubt it, but, it's possible. Since I don't like barrel bands anyway, if thIs one is easily removed, it might be a worthwhile test. Whether a band supports the actual barrel, or a shroud, some of them will shift their pressure enough to cause problems. But it's usually not as predictable as this sounds. Just something to probably eliminate.
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Most/many barrel bands are anchored on the pressure tube. Some are "free-floating" around the barrel/shroud. In either case, as the pressure tube pressure rises, it flexes and expands. This WILL cause the barrel band to move. In the case of barrel band that are in constant contact with the barrel/shroud, there WILL be a noticeable change in POI.
For those barrel bands that are "free floating", there *may* be a noticeable change in POI if the barrel/shroud ever comes into contact with the barrel band due to the flexing of the pressure tube.
Just my own observations from my limited experience with PCP airguns. However, this has held true for both types of barrel bands for me.
YMMV
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I had to work with the barrel band on my Fortitude Gen2 to *make sure* that the shroud was *free floating*. Once I did that, I have had no problem with POI change due to whatever pressure is in the pressure tube. When I got the gun new, the shroud WAS touching the barrel band and that DID cause POI shifts due to pressure tube changes.
p.s.
JFYI, the Fortitude is designed to have a free floating shroud/barrel. If the shroud is touching the barrel band, there will be problems. Same goes for any other airgun that uses a free floating barrel/shroud and probably worse for those where the barrel band is not *free floating*. Just make sure the barrel/shroud has good and equal clearance all around and that *should* take care of any problems with the flexing of the pressure tube.
Unless, it has a flimsy fore stock like the Fortitude. In that case, you will STILL experience POI shifts (usually UP) if there is much pressure placed on the fore stock (where you would mount a bipod). Even using a rest, if the end of the fore stock is placed on the rest and ANY pressure is placed on it, the POI will go up because the pressure tube WILL come into contact with the shroud/barrel.
I have learned to place the Fortitude on the rest as close to the trigger as possible to negate/eliminate this problem.
Again, YMMV
I am just talking about my own experience with the Benjamin Fortitude Gen2...
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With airguns, a chronograph is essential if you want to tune your airgun. However, you don't have to have an expensive chronograph. This is what I use. It is cheap, works consistently and accurately.
https://www.amazon.com/VIKKA-Precision-Chronograph-Velocimetry-Chargeable/dp/B08DRJ3JW7/ref=sr_1_89?crid=1XER1OF6Y5ZGQ&keywords=air+gun+muzzle+velocity+meter&qid=1645827125&sprefix=airgun+muzzle+velocity+meter%2Caps%2C104&sr=8-89
Mine was sold under a different name, but this one is still the same.
It works well, even in total darkness without an external light source. I highly recommend it!
I just wish there was something like it MADE IN THE USA at an affordable price... (heavy sigh)
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Timothy8507, on my Avenger, I discovered that my Picatinny rail on the Avenger stock was affecting my POI. I later removed the mount from the wooden stock and JB welded it to the stock and wiped off the excess before it cured. I had an arcu-swiss plate mounted and secured to my tripod. It was causing too much flexing of the tube and shroud clamp, affecting my POI. I later put a barrel clamp on the long air tube and shroud.
Now I mostly use my death grip platform or bag.
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