N/A Barrel harmonics or ideal pellet speed.

[Caliber 22]

Many times I hear / see people say the pellet like a certain speed. As an example they will say a certain pellet like 870fps and 910fps where it shoot accurately but not 890 fps where it is unstable and less accurate. Now, it is obvious that 890 is between the other two figures. If you shoot at 910fps, within a few meters the speed will drop to 890fps where the pellet is according to that logic unstable, but still it shoots accurate.

What I always say is that it is not that the pellet is unstable at the example of 890fps, but it is the barrel harmonics that is different in the two scenarios. A good pellet will be stable at any speed as long it is below or well below the speed of sound, depending on the pellet.

The same way we do load development with PB rifles, we do tuning with PCPs and that is to get the barrel harmonics and time of projectile exiting the barrel working together.

What do you say about it?

 

[nomojo65]

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.

 

[Caliber 22]

even in pellets within different lot numbers of same weight and brand.

That I did experience a lot, also with .22LR. That is why competitors lot test.

 

[dizzums]

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 ..

 

[beerthief]

with springers we tune for FPE so how does that fit in ?

 

[dens228]

with springers we tune for FPE so how does that fit in ?

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.

 

[Caliber 22]

with springers we tune for FPE so how does that fit in ?

I don't know anything about springer tuning but to test different pellets to see what shoots best.

 

[beerthief]

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.

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 .

 

[Caliber 22]

 

[Caliber 22]

 

[dens228]

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 .

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?

 

[JimD]

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.

 

[nomojo65]

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!

 

[elh0102]

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!

 

[Caliber 22]

If you don't find the right combination, well, there's an excuse for a new rifle!

Then I will never find the right combination.

 

[Caliber 22]

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.

With my PCP the H&N 18gr shoots the best, but not matter how I adjust the JSB 18gr never shoots good. However, the JSB 13gr and 14 gr shoots good if I adjust for that.

When I adjust / tune any rifle and I do tune for other people as well, I start with the highest speed for that regulator setting and bring the speed down 1/4 turn at a time. The groups will get smaller then larger and then smaller and larger ..... and so on. As I go through the adjustment the groups will shoot high and then low and then high .... in combination of group size, according to the hammer setting, all without touching the scope setting. That tells me that the pellet exits at different positions of the barrel harmonic curve. I then choose the best group and work around that setting with smaller hammer adjustments to find the smallest group around that settings. Sometimes I try another course setting that shows potential and work around that and compare best groups. Then over to the next pellet and start all over again. I learned to make notes about the progress. After all that I will do final zero of the scope and test the speed to enter into Strelok.

Different pellets will shoot best at different speeds from different rifles. That again tells me it is not so much about the speed but the combination of the system with barrel harmonics and exit time as the leading cause.

All this I learned from Steve from AEAC and others.

 

[dens228]

I've pretty much stuck with JSB's. They've always shot well out of my rifles.

 

[JimD]

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.

 

[TYLERHASKINS2]

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.

 

[mubhaur]

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