Pont of impact drop above regulator pressure

[C4boom]

So I just got a Air Venturi Avenger stock settings. If I shoot mine past 3400 psi things like this happen ( reg presure looks to be 2900). The hole in the center is my aim point at 100 yards. I would think it wouldn't be a issue till under regulator pressure. Can some one explain . If I keep the presure over 3400 its not bad. 

The mess on the right is my niece lol

 

[Vetmx]

Fire an entire shot string over the chronograph and you will have your answer. I also wouldn’t trust the gauges on your gun. A bum gauge can have you chasing your tail for a while.

 

[nervoustrig]

Tell me if I'm understanding you correctly...it's shooting low and then begins shooting higher as the pressure falls? If so, that means you need increase the hammer spring tension (or reduce the regulator pressure). The root cause is the hammer is not hitting the valve stem hard enough to fully open the valve. It can't overcome the pressure that is holding the valve closed, the result being the gun is operating at a state of partial valve lock.

Then when you keep shooting and the pressure continues to fall, it eventually gets low enough that the hammer can knock open the valve fully (more air is released) and you get a higher velocity and a higher point of impact.

The solution is to gradually increase the hammer spring tension until the velocity no longer increases. Then back off slightly until the velocity falls to 95 - 97% of the peak. So for example if it tops out at 900fps, back off the hammer spring tension until the velocity drops to somewhere in the range of 855 - 873fps. In so doing, you'll get a consistent velocity until the pressure has fallen well below the regulator's setpoint, and then a gradual rolloff from there. This state of tune will also improve the extreme spread.

 

[pcwhite]

At 100 yards a lot of factors come into play. Wind, pellet shape, slight fluctuations in trigger pull, breathing wrong, etc. Not necessarily the regulator pressure. Your shooting looks better than mine.

 

[knifemaker]

N. Trig is on the money. However, without a chrony reading or knowing the projectile, it may be something completely different.

Here's what I mean, with heavier pellets, and particularly slugs, an ag can show the same behavior of a Mangum PB Handgun. 

The faster the projectile, at a short range, the lower the impact. Lighter loads with hit higher. 

Why, because a slower, heavier slug or pellet will be traveling down the barrels' length slower and exit at a higher zenith of the barrels muzzle in relation to the target due to exiting the muzzle later in the recoil cycle. Hence, hitting at a higher point on the target than a faster projectile of the same weight. 

This is why a Chrony is needed. It is a must for tuning. 

Knife

 

[C4boom]

So looks like my first step will be getting a chrony so that I have an idea of the force applied on the pelet. I come from the powder Gun world where I generally start at a 100 yd So this is all new to me. I am Lucky to have a 150 yd range at my house . So it allows me to do a lot of testing. I think there may have been a misunderstanding in what I was saying.I was at 3400 PSI in the reservoir. I just checked and my regulator is supposedly set to 2600. My shots start at the far upper right and end at the far lower right . There are a few fliers in there also as you can see. I shot from 3400 PSI to 2800. I am using air arms Diabolo field heavys 18 gr in 22 cal . I believe I lucked out As it was the 1st Tin of pellets that I purchased and they seemed to shoot marvelously. I did sort them though as I started with 250 pellets and after examining and measuring each one was down to about a 126. I used the rest for sighting in at 20 yd and for pest control. I believe I'd like to tune the rifle to be at around 875fps to 850fps which would be more optimal for the standard pellet shape. I'm just wondering If the gauge is off and I was shooting actually below regulator pressure or if something else is going on. 



Thank you all for your time

Boomer

 

[elh0102]

Yes, you definitely need a chronograph in tuning your rifle. An observation, if you are correct in the reg set point, that is almost 180 bar, which seems very high, although I am not familiar with this rifle. If you can adjust the hammer spring tension to obtain the balanced tune described above, you may find that your shot count is lower than you want. If so, you may want to lower the reg setting. Nervoustrig is probably totally accurate in his assessment, so maybe a combination of a lower reg set point and hammer spring adjustment will give you the desired result.