Tuning a PCP

[Vetmx]

Even the H&N 18 does not shoot as presice at 890fps as 940fps out of this rifle, no matter the pressure or tune. I did try a lot

Last year a had a pellet shooting M3 500mm. I noticed the exact same thing with H&N 27gr hunting pellets. They did ok just under 900 fps but were phenomenal at 935-938fps. And that was out to 100 yards. So that’s where the gun stayed until I changed things up. Like Trucker said, it’s your barrel. Not external with harmonics but internally. Barrel harmonics with a pellet gun that has a solid barrel on it might be getting overemphasized lately.

 

[EddieBoatner14]

Yeah, it's pretty normal for some rifles and pellets to shoot best well below the max speed.

 

[AirNGasman]

Question: Is this normal for some rifle / pellet combinations to shoot precise that much below the max speed, way below the knee?

"Normal is a relative term, often in the mind of the beholder, and especially as pertains airguns, airgunning and airgunners." - Abby Normal

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[Caliber 22]

Barrel harmonics with a pellet gun that has a solid barrel on it might be getting overemphasized lately.

I can see how barrel harmonics has an influence on this rifle. With any pellet, starting from a certain speed and turning the hammer up or down at small increments, the POI will go lower then higher and repeat the process, like a continuous wave. I found that the precision of the best shooting pellets and speeds will be on the antinodes, meaning the high or low POI as I adjust the hammer. The barrel is quite thick, about 15 or 16mm. I cannot measure now as the shroud is on.

 

[Vetmx]

I can see how barrel harmonics has an influence on this rifle. With any pellet, starting from a certain speed and turning the hammer up or down at small increments, the POI will go lower then higher and repeat the process, like a continuous wave. I found that the precision of the best shooting pellets and speeds will be on the antinodes, meaning the high or low POI as I adjust the hammer. The barrel is quite thick, about 15 or 16mm. I cannot measure now as the shroud is on.

Well if you believe, then you have another rabbit hole to go down if you want to try to influence it. Will it be worth it? Only you can determine that.

 

[Caliber 22]

If there are no barrel harmonics, why does barrel tuners and indexing work to improve presision on some pcp's and even break barrels?

Here is a video showing a break barrel vibration.

 

[Smitty911]

If there are no barrel harmonics, why does barrel tuners and indexing work to improve presision on some pcp's and even break barrels?

Here is a video showing a break barrel vibration.

Cool video, would have been nice to capture the pellet leaving or frame by frame to correlate the movemetnt.

Smitty

 

[Caliber 22]

There are other videos about air rifle barrel harmonics I saw before. This is only the first one I found and posted.

There are some videos about air rifle barrel tuners as well, do a YT search and you will find it.

I never used it before as I prefer to tune the rifle and take note of the influence of different weather conditions and adjust accordingly. Like the previous time I shot it was 32°C and today it is 18°C so the speed is average 25fps lower as it is with pcp's. It did not make much of a difference on POI as the hammer also causing vibrations is still the same if not a little bit stronger because of the lower temperature.