Tune for grouping in sub12?

GrandPA

GrandPA

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Please, before jumping to condem for mentioning the word tune, I am not asking for advice on how to, nor should you give advice on tuning on a open thread.

That said, here we go, I have watched several videos non UK spec or laws and see the difference power can have on grouping, not always for the better.
So knowing that with UK limits we generally are at a lower than suggested speed already, has it been proven or even worth it to try tuning sub12ft rifles for grouping given that we already cannot achieve suggested optimal speeds?
 
If you look at some of @1260engineer posts, you'll see he does set his guns power to suit different pellets, very successfully, from my experience of extensive pellet testing and experimentation, I've come to the conclusion that "pellet fussy barrels" is a myth and it's down to the power plants effect on the pellet, hence two "identical" guns will like different pellets, I have observed two HFT500S that swapped barrels and thier preferred pellet stayed with the gun, not the barrel..... what most of us mortals have to do , is find the pellet that our gun likes as a whole, not just the barrel, unless you have one with easily adjustable power (within legal limits). I've found between 10.5 and 10.8 ft/lb works best for one of my guns.
From what ive observed and read about other people experimenting with adjustable air strippers, has shown that these can also help with accuracy. ... but this will open up another can of worms, as to what is "accuracy"?... for me it's a sub 6mm grouping at 25 yards.... others will be happy with 1/2" at the same distance.... but I benchrest competitively (local comp), it's all about perspecive!! How deep down the rabbit hole do you want to go?😁
 
I don't know if there is a direct correlation between tuning and accuracy. My tuned 97 felt and sounded better to shoot but was already very accurate. Does tuning reduce recoil? I'm not sure but if it does that may improve accuracy. I did not notice any improvement. If a gun is more pleasant to shoot perhaps you shoot it more so greater accuracy is achieved that way. i.e. not directly

Al
 
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Yes indeed. "Tuning" for better accuracy is something of an open secret.
Accuracy can be improved by adjusting (experimenting) with the velocity of the pellets as they exit a barrel.

However, we don't have a huge amount of power to play with (sub 12), so the thought if actually reducing it doesn't sit well with some folk.
Meanwhile, other folk don't mind a slight reduction in power if the accuracy is vastly improved.

At the end of the day, it comes down to what is important to us.
Some want 11.99 ft.lbs proudly showing on a chrono. . Others are more content with sub 5p-size groups at 50 yards.
 
As above, it’s perfectly fine to talk of tuning as a way of improving accuracy NOT power.

I feel my 98 is a little hot running on 11.2ftlb. I’m going to open her up at some point to see if I can get her around 10.5. Many on here claim that’s a sweet spot.
 
I think it's different between springers and PCPs. PCPs find the best speed for your pellet sub-12. Many hft and ft shooters tune PCPs to around 777fps with 8.44 pellets but that's more about a safe margin power wise and a lot of rifles may be a tad more accurate a bit slower. With a springer tune to best shot cycle as they are then easier to be accurate with although some springers shoot remarkably well with a harsh cycle.
Broadly somewhere between 10.5 and 11 seems to be good for many pcps and springers for accuracy but in airguns and particularly springers there are few rules and many guidelines....
 
Worth viewing some sub12airgunners videos on YT.

There are rifles using different systems that are taken apart and optimised for accuracy - not power.
Hammer weight and size, spring strength, regulator tuning, barrel cleaning/polishing, the hole starts to get deep quickly.
There are no quick fixes, what works in one rifle may not work in another.
 
I found my hft5 improved its accuracy with its already best pellet as I dropped fps and found 745>755 fps its sweetspot with jsb express, but exacts needed 775. My Kral running an hft5 barrel needs much different speeds

There’s so much to look into, reg pressures, plenum volume, barrel lengths, valve and port sizes, silencing, pellets, and the nut on the trigger
 
From my reading around I would say it's also worth noting that in countries where you are allowed more power in general people tuning for accuracy are not using much more speed than we are (around 900fps appears to be a ceiling for diablo pellets) but they use heavier ammo at not dissimilar speeds to us...
 
For PCPs an influential factor is barrel harmonics; so muzzle weights, barrel bands and MV can be adjusted. For springers, barrel harmonics are less influential than shot cycle. I see various opinions expressed about optimum MV for a pellet type but the pellet itself doesn't determine the optimum, it's mostly the position and direction it leaves the barrel and, subsequently, how its flight is affected by external forces.

I'm not sure what you mean by UK limits being below suggested speed. UK limits prevent us from achieving the maximum sub-sonic velocities before which pellets dramatically lose stability but that's not the same as optimum velocity for good grouping.
 
GrandPA said:
Please, before jumping to condem for mentioning the word tune, I am not asking for advice on how to, nor should you give advice on tuning on a open thread.

That said, here we go, I have watched several videos non UK spec or laws and see the difference power can have on grouping, not always for the better.
So knowing that with UK limits we generally are at a lower than suggested speed already, has it been proven or even worth it to try tuning sub12ft rifles for grouping given that we already cannot achieve suggested optimal speeds?
Click to expand...
When I had my s410 fully service by Kev Jackman ( 2x world champion) and air arms guru IMHO, he actually lowered the power to 10.2 for 8.44,.

I was shocked at 1st as I, like many thought we should strive for high 11s.

How wrong I was, it grouped better than before.

I'm not saying this would be the result for all rifles but deffo made a difference on mine
 
I was under the impression that "tuning" was more about making an air rifle shoot consistently, accurately and in the case of boingers with less recoil. Unless you have an FAC to cover your rifle the 12 ft/lbs UK limit applies to all. The 777 fps with 8.44 grain pellets "rule" was advised for HFT shooters because if checked with a JSB 10.34? grain pellet it will still be a tad under 12.
 
To put it simply, because we're limited to such low power, it's often best to tune the rifle to just under 12fpe using the most efficient pellet (this usually means a JSB heavy of some derivative for a PCP from my experience) and then find the pellets which are most accurate in that state of tune. This is mainly for hunting to deliver the most energy to the target whilst remaining as precise as possible and staying under the 12fpe limit should the plod decide to inspect the rifle.

For higher level target shooting, it's absolutely worth tinkering with pellet speeds as power at the point of impact isn't quite as critical. I'd put that level of tweaking in the same boat as sorting pellets. I have no doubt it's part of a benchrest shooters way to really dial it all in.
 
Some threads worth reading if you want more understanding of the factors influencing consistency of trajectories:

J

Thread 'How physics can help us understand and exploit barrel vibrations, Part 1'

This is my first post in this forum and I just wanted to let you know that it's long and technical. However, the ideas are fairly basic and the most of the story is told by the figures. I learned a lot in the process of writing this post and hope that you find the long slog through it interesting and perhaps even enlightening!



My job as an experimental physicist is to come up with new measurements to observe phenomena that are hard to see. This gives us new insights and a better understanding of how the world works. The same can be applied to spring piston airguns, which can be very...
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Ballisticboy

Thread 'Long Range and Pellet Spirals'

A short while ago, I started looking at the problems with firing pellets at high speeds and long ranges. The data was all at FAC level speeds, where there are known difficulties from pellet spiralling. Having produced a lengthy thread on some US forums showing tendencies for spiralling, I have gone on to see what happens at sub 12 FPE speeds, specifically in .177 calibre.
The pellet I have chosen is the JSB 10.34 grain Heavy pellet. This is not because the JSB pellet is particularly bad, it is just because I happen to have more data on that than I do on most other pellets. A .22 scaled up...
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Ballisticboy

Thread 'One Reason Lead Free Pellets May Be Less Accurate Than Lead Pellets'

Following some recent threads, I thought this post from the previous forum may be of interest or use in helping to understand why lead free pellets seem to be so much less accurate than their lead equivalents. I used tin for the modelling, but zinc pellets would give much the same result, as the densities of tin and zinc are very close to each other compared to lead.

I have been carrying out a bit of simulation of tin pellets based on two current lead pellet designs in .177. The two designs chosen are the 8.4 grain AA Field pellet and the early JSB Heavy pellet with the cylindrical...
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Ballisticboy

Thread 'Pellet Aerodynamic Stability'

Looking at comments in some of the recent posts regarding the way pellets are stabilized, I thought I would reproduce this thread from the old forum to try to clear up some misapprehensions.

In a video by one of the leading YouTube air rifle video producers, he went to great lengths to explain pellet aerodynamic stability and how it differs from slugs. Unfortunately, he just repeated everything else which has been said before. Fig 1 below is close to one of his main diagrams and is typical of many diagrams used to explain drag stability on pellets.

pelsta2.webp

Fig 1

The claim is that...
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It's easier for most of us to find a pellet which suits the gun than tuning a gun to a specific pellet. Anti-tamper devices restrict simple power adjustment and changing MV. Even with ATs removed it's often more complicated than changing one parameter due to Interdependencies and the need to balance different settings. Apart from fixing weights on the barrel, most other changes require disassembly, reassembly and testing, which are extremely time consuming.
 
Thank for your replies, you have just reinforced my understanding as an engineer. Time and again you can see someone at the range talking about it's 11.5ft/lbs with such and such pellet, or people asking in the for sale section how much power is it?
When I rather know what is it's preferred food and how tight are the groups at "x" distance that you shot the rifle at.
Yes I understand pest control want power but it needs to be in the right spot first. The fact that some of you same competition shooters would use 10.something also confirmed that speed is a bigger factor than just trying to reach the knee of the curve as close as you can to 12ft/lbs, again thanks for the comments.
 
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