N/A .
- Thread starter Caliber 22
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I believe the majority of tuning in a airgun is pellet speed as it leaves the barrel ( timing ) for that particular pellet. So that timing ( speed ) will vary with weight and brand of pellet even in pellets within different lot numbers of same weight and brand.
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i think youre about right on, but to arrive at the right harmonic youll read it by pellet speed .. i usually do everything backwards and try to get the speed as high as reasonably possible and then tweak other things to tighten them up to an acceptable level ..
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Since fpe is based on speed and weight if you know the pellet weight you’ll know what speed you need for that fpe so you tune for speed.
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so i guess i have been backwards ? i tell the tuner what FPE i want and the smoothest shot cycle , then find the pellet the gun likes for best accuracy . Then cronie it to find the speed .
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I don't want to mess around with finding pellets. I've had good luck with JSB's. They seem to fly the best for me at various speeds. How do you know the fpe without the speed? Unless I'm reading your post wrong?
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I have some PB experience and some airgun experience but I can't claim to be an expert at either. But I think that the much much higher pressures in PBs makes the barrel harmonics much more of an issue for PBs. In airguns I think the barrel reacts to different pellets differenct but I think the vibratory response is more from the entire gun. The hammer, the valve, and the pellet/barrel reaction. The ignition factors in a PB probably play a role too but are overwhelmed by the huge pressure pulse. Our much milder pulse and more complex "ignition" system makes a difference IMHO.
I also find the tune or pellet speed to be a secondary factor to finding a pellet the airgun likes. I find the pellet first, then the tune or speed it likes. I do not believe that all copies of any gun will prefer the same pellet. There are probably tendencies but also exceptions. Pellets that shoot well at 750 fps also shoot well at 850 fps in my experience. But they may shoot better at one speed than another. Since I think airguns are individuals I also don't think there is a particular velocity that will work best for that pellet in all guns.
It seems like most of the time, pellets that are accurate in my guns also have a lower ES and std dev than pellets that are less accurate. To me this is just an indication that the whole gun likes that pellet, not just the barrel. Since my shooting skills are not totally dependable, I also look at the ES and std dev for an indication what pellet the gun likes. The pellet still has to group but might get another try if the ES looks good.
I test H&N and JSB and sometimes others. More of my guns like H&Ns the best than like JSBs the most.
I also find the tune or pellet speed to be a secondary factor to finding a pellet the airgun likes. I find the pellet first, then the tune or speed it likes. I do not believe that all copies of any gun will prefer the same pellet. There are probably tendencies but also exceptions. Pellets that shoot well at 750 fps also shoot well at 850 fps in my experience. But they may shoot better at one speed than another. Since I think airguns are individuals I also don't think there is a particular velocity that will work best for that pellet in all guns.
It seems like most of the time, pellets that are accurate in my guns also have a lower ES and std dev than pellets that are less accurate. To me this is just an indication that the whole gun likes that pellet, not just the barrel. Since my shooting skills are not totally dependable, I also look at the ES and std dev for an indication what pellet the gun likes. The pellet still has to group but might get another try if the ES looks good.
I test H&N and JSB and sometimes others. More of my guns like H&Ns the best than like JSBs the most.
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There are so many factors in tuning air rifles “and trust me I’m no expert” it’s not just the harmonic's of the barrel it’s all the influences prior to the pellet leaving the barrel that contribute to these harmonics, such as how hard the hammer has to hit the valve to overcome the Reg. Set psi, how long this interaction takes etc.,etc. another big factor is finding the correct reg. Psi that allows the pellet to achieve set velocity without wasting air which will effect the pellet after it leaves the barrel. Some of my thoughts, not necessarily science!
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The variables involved in achieving accuracy are almost infinite. I suggest that you first need to determine your priority goal. It might be a certain fpe, a range of velocity, a certain pellet, etc. With that goal in mind, you manipulate all the variables within your control to find the best combination. There are no rules, tables, or formulas that will do the work for you. Just go to the range and shoot. If you don't find the right combination, well, there's an excuse for a new rifle!
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My process is very similar to Caliber 22 but I am lazier. I do not tune for each pellet. I shoot a 5 shot group or two or three with each pellet and decide which ones the gun likes and doesn't like and then I fine tune one or two to decide on the "winner". I've tried shooting pellets the gun doesn't like much at multiple speeds to see if I can get it to like them. Didn't work at all. So I look at the "speed" or "tune" or whatever you want to call it (I prefer tune) to be a secondary factor and just assume none of my rejected pellets could become the favorite. I might be missing something but I doubt it.
I find the knee of the curve with one pellet and get the hammer spring setting a reasonable amount slower first. Then I start testing pellets.
I find the knee of the curve with one pellet and get the hammer spring setting a reasonable amount slower first. Then I start testing pellets.
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I think I agree, I noticed in my Benjamin Akela .177, the pellets (all of them) really liked that 880-870 range, but my airforce TalonP (12 inch barrel 25 caliber) doesn't really care. the barrel on the airforce gun is incredibly rigid and secured very tightly to the frame, where the Akela is completely free floated. with the talonP I usually shoot for groups and adjust the power wheel until the groups are good and call it a day, the last time I did that the groups were great and the pellets were shooting around the 930 FPS range, so it would make sense that its a barrel thing more than a pellet thing.
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I understand that in PB our options for tuning are limited to the weight and shape of the projectile and the energy with which it will start the travel.
While in PCP airguns, now a days we have control over regulator pressure, hammer spring tension، valve devel, valve return spring strength and adjustability, solid vs FX liner system type barrels etc.
If we add in the pellets in the above, there becomes almost unlimited combinations.
Each combination will give different accuracy. The best accuracy may be achieved at some unknown fps before the transonic zone is reached.
For extreme accuracy from any projectile, it's the projectile that dictates us about the right combination.
If we ourselves decide anything in the above mentioned factors, we cannot achieve the best possible accuracy.
Twist rate is another factor that I didn't mention above.
Regards,
Bhaur
While in PCP airguns, now a days we have control over regulator pressure, hammer spring tension، valve devel, valve return spring strength and adjustability, solid vs FX liner system type barrels etc.
If we add in the pellets in the above, there becomes almost unlimited combinations.
Each combination will give different accuracy. The best accuracy may be achieved at some unknown fps before the transonic zone is reached.
For extreme accuracy from any projectile, it's the projectile that dictates us about the right combination.
If we ourselves decide anything in the above mentioned factors, we cannot achieve the best possible accuracy.
Twist rate is another factor that I didn't mention above.
Regards,
Bhaur
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I like to try to understand why things are the way they are, like, why do I miss so much? I can understand that if a barrel points in slightly different directions as it harmonically wobbles about, then I'll miss a little less if I can time the pellet to leave around when the barrel is changing direction. The barrel will point for a longer time in the same direction while it decellerates, stops and accelerates again, whereas mid-swing the barrel is changing direction rapidly. And I kinda understand that timing both the pellet exit and the harmonics in general depends a lot on pellet speed (and thus weight and power setting).
But how about pellet stability and spiraling?
Ted's Holdover has a video where he shoots the same gun at 1100 vs. 800 fps, and sees spiraling at the higher speed:
There is another where he sees spiraling when the barrel is dirty:
I thought of these when I shot some otherwise accurate pellets out of an otherwise accurate barrel, and watched them spiral a foot or more at 50m (I think in my case they were going too slowly).
Maybe speed and dirty barrels are related, maybe not.
But anyway, is that harmonics with the barrel? Or something about the pellet and its airspeed, independent of the barrel?
- Mike
But how about pellet stability and spiraling?
Ted's Holdover has a video where he shoots the same gun at 1100 vs. 800 fps, and sees spiraling at the higher speed:
I thought of these when I shot some otherwise accurate pellets out of an otherwise accurate barrel, and watched them spiral a foot or more at 50m (I think in my case they were going too slowly).
Maybe speed and dirty barrels are related, maybe not.
But anyway, is that harmonics with the barrel? Or something about the pellet and its airspeed, independent of the barrel?
- Mike
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The pellet going unstable and spiraling is not the harmonics of the gun, it is the spin rate of the pellet which is closely related to the pellet speed but not exactly the same thing. The twist rate of the barrel plus the velocity of the shot determines the spin rate. Spin it too fast, especially if it is windy, and the pellet may not be stable. In light wind, low to even mid 900 fps may shoot great. But when it gets windy, the pellet may become unstable. I tune to stay under 900 fps most of the time because I want the pellet to stay stable even when the wind is blowing. My target for my current "new gun" is 875. My most recent string averaged 880 fps so it may stay there - needs a bit more testing.
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