Tune for grouping in sub12?

As an extreme, if you had 2 similar guns of the same make, one with power adjusted to the limit and one restricted to under 6 ft-lbs, which one do you think would be the most accurate over a short distance?
 
One of my S200 rifles is running at just below 8ft.lbs.
This is how it was when I bought it (second hand).
I intended to bring it up to a higher power output but after shooting it and seeing the results, I shall leave it alone.

IMG_20221228_123608.webp
 
Stockscrew said:
As an extreme, if you had 2 similar guns of the same make, one with power adjusted to the limit and one restricted to under 6 ft-lbs, which one do you think would be the most accurate over a short distance?
Click to expand...
Indoors..the one in the best shooters hands.

Outdoors in real weather? The well set up sub12.
 
Tillygti6 said:
Indoors..the one in the best shooters hands.

Outdoors in real weather? The well set up sub12.
Click to expand...
I cannot agree with this as I had a 177 Titan Manitou set up for bell target at 6fpe which from a bench rest would put the pellet cleanly through the 10mm hole every time at 15 yds. When it was reinstated to 11fpe for hunting it was shot at the bell target from the same range, same sights and I found although the pellet went through the hole many of the shots clipped the edge of the hole and left a grey smudge, yet at 30 yds it produced nice cloverleaf groups. In this trial, the 6fpe version of the gun proved to be most accurate at around 560fps rather than at 780fps.
 
Stockscrew said:
I cannot agree with this as I had a 177 Titan Manitou set up for bell target at 6fpe which from a bench rest would put the pellet cleanly through the 10mm hole every time at 15 yds. When it was reinstated to 11fpe for hunting it was shot at the bell target from the same range, same sights and I found although the pellet went through the hole many of the shots clipped the edge of the hole and left a grey smudge, yet at 30 yds it produced nice cloverleaf groups. In this trial, the 6fpe version of the gun proved to be most accurate at around 560fps rather than at 780fps.
Click to expand...
It is not unknown for powder burners to give tighter groups at 100 yards than they do at 50, and suspicion falls on spiralling.

Perhaps @Ballisticboy could offer some of his wisdom on the theory.
 
Stockscrew said:
I cannot agree with this as I had a 177 Titan Manitou set up for bell target at 6fpe which from a bench rest would put the pellet cleanly through the 10mm hole every time at 15 yds. When it was reinstated to 11fpe for hunting it was shot at the bell target from the same range, same sights and I found although the pellet went through the hole many of the shots clipped the edge of the hole and left a grey smudge, yet at 30 yds it produced nice cloverleaf groups. In this trial, the 6fpe version of the gun proved to be most accurate at around 560fps rather than at 780fps.
Click to expand...
I can prove it🫣 it's all on film too so you can see for yourself.

My 9015 at just under 25yds outdoors in next to no appreciable wind will match the groupings of the very best Olympic 6ftlb 10m target rifles (of which there are thousands of 9015s) when they are tested at only 10metres.

For reference I'm talking sub 5.5mm groups.

This is why I went to the expense and time to build a test rig along similar lines to what the olympic teams use for batch testing pellets.
I'm certainly not accurate enough to match or better the dispersion of the 9015 but also now have benchmarks and have an average measurement of my own natural wobbles and how that effects my groups.

It also turns out I can outshoot my streamline, rti and katran.



It's super interesting and once I got a handle on how to get the rig set up ,will be invaluable going forward for myself and for all of us,as I'll share all the findings.
 
Nomads HFT said:
It is not unknown for powder burners to give tighter groups at 100 yards than they do at 50, and suspicion falls on spiralling.

Perhaps @Ballisticboy could offer some of his wisdom on the theory.
Click to expand...
Not uncommon by all accounts with the boys slinging slugs(not pellets) at higher powers, I guess as they share similar ballistic traits as bullets it could be a thing
 
I bought a left-hand Steyr Olympic pistol (electronic trigger; it was cheap(ish) because it was L/H) which came, in true Germanic fashion with a test target from the factory. The five-shot "group" just looks as if they put one pellet through the target and called it a day. Clearly it was clamped in a vice for the test, but even so I don't think there's much point in trying to tune that pistol!

P.S. Have you seen the Turkish bloke who looked as if he was just a spectator and picked up someone else's pistol to "have a go"?
 
WRT tuning rifles, I don't feel that I can do that to mine; they range from 10 FPE to 11.3 FPE.

The trouble is, wouldn't an honourable effort to tune a rifle to obtain maximum accuracy at lawful power levels, open up the owner to accusations of "having a gun which can exceed lawful limits"? I personally feel that it's monstrous that the police can "seize" a rifle after having worked on it to push it over the limit, when it was under the limit when "seized".

My opinions won't hold any weight in a court, so I'm not touching mine, but I would really welcome the opinions of others.
 
Tillygti6 said:
... I went to the expense and time to build a test rig along similar lines to what the olympic teams use for batch testing pellets.
I'm certainly not accurate enough to match or better the dispersion of the 9015 but also now have benchmarks and have an average measurement of my own natural wobbles and how that effects my groups....

It's super interesting and once I got a handle on how to get the rig set up ,will be invaluable going forward for myself and for all of us,as I'll share all the findings.
Click to expand...
Will be interesting following your progress.

One thing you might consider is the dissipation of excess energy through the action and mountings: whether the rigid mounting causes additional vibration in the barrel. Intuitively, I think a damped linear bearing might produce tighter groups. It would be interesting to measure movement in the barrel, perhaps by dial gauges or high speed photography?
 
Stockscrew said:
I cannot agree with this as I had a 177 Titan Manitou set up for bell target at 6fpe which from a bench rest would put the pellet cleanly through the 10mm hole every time at 15 yds. When it was reinstated to 11fpe for hunting it was shot at the bell target from the same range, same sights and I found although the pellet went through the hole many of the shots clipped the edge of the hole and left a grey smudge, yet at 30 yds it produced nice cloverleaf groups. In this trial, the 6fpe version of the gun proved to be most accurate at around 560fps rather than at 780fps.
Click to expand...
Same pellets ? Different bullets " go to sleep" @ differing distances @ different velocity.
 
BallisticBill said:
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...
  • Like
  • Love
  • Wow
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...
  • Like
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...
  • Like
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...
  • Like
  • Love

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.
Click to expand...
Crikey Bill you got nothing to do mate 😂😂🤣😂🤣
 
BallisticBill said:
Will be interesting following your progress.

One thing you might consider is the dissipation of excess energy through the action and mountings: whether the rigid mounting causes additional vibration in the barrel. Intuitively, I think a damped linear bearing might produce tighter groups. It would be interesting to measure movement in the barrel, perhaps by dial gauges or high speed photography?
Click to expand...
Thats exactly why I tune my rifles clamped solid with a couple of clocks on them . the tuning then consists of eliminating the vibrations generated by the moving parts which transfer and create the barrel harmonic wave . tiz very simple logic .
then when you take the rifle out of the clamps there is next to no harmonic wave and especially that will affect a 16mm barrel 🙂
I got the idea from shooting my springers where different holds change the way the rifle reacts . hence the clamping amplifys everything in the pcp so i can see it and sort it .
 
Mark Palmer said:
As fascinating as I find your technical posts Bill, they are way above my pay grade/understanding! I often have to coerce my brain to crawl back into its box from my shoulder!!🤣🤣🤣👍
Click to expand...
Sometimes mate i simplifie things by making rifles do bad things. it makes it much easier to figure out the whys. wheres and how to's.
 
1260engineer said:
Thats exactly why I tune my rifles clamped solid with a couple of clocks on them . the tuning then consists of eliminating the vibrations generated by the moving parts which transfer and create the barrel harmonic wave . tiz very simple logic .
then when you take the rifle out of the clamps there is next to no harmonic wave and especially that will affect a 16mm barrel 🙂
I got the idea from shooting my springers where different holds change the way the rifle reacts . hence the clamping amplifys everything in the pcp so i can see it and sort it .
Click to expand...
I know you are tuning the action to minimise vibrations which would otherwise induce harmonic waves in the barrel. I'm not clear on what you are doing to change the harmonics of the barrel - amplitude, frequency and position of nodes - and how these are linked to choice of pellet. My question is to what extent you are tuning the rifle generally rather than to a specific pellet?

Related to this, I've often wondered about how a solid mounting and same settings can be used as QC for different pellets when we know different guns (in a given tune) prefer different pellets. The fact that one gun doesn't perform with a particular batch of pellets doesn't necessarily show there is anything wrong with the batch, or that it won't perform well in other guns.
 
BallisticBill said:
Will be interesting following your progress.

One thing you might consider is the dissipation of excess energy through the action and mountings: whether the rigid mounting causes additional vibration in the barrel. Intuitively, I think a damped linear bearing might produce tighter groups. It would be interesting to measure movement in the barrel, perhaps by dial gauges or high speed photography?
Click to expand...
absolutely mate. Currently it's affixed to the laminate mounting block exactly as the action sits in the current highest scoring 9015 in European world rules bench rest. Matt at airability 😉

I'm absolutely certain though that there's further gains to be had with the density of the stock(species of wood I guess we could say) and also the volume/mass of the stocks.

I'm experimenting with various other mounting arrangements and have yet to see any meaningful improvement, not that I can measure incredibly accurately other than by feel anyhow.

It's really hard to test as deeply as I'd like, honestly it comes down to the time and costs. Now the yt channel has started to sustain itself it does give me a little budget to try these things and buy the stuff and ofcourse everything I learn gets shared for you all to ponder and hopefully we can all push the sport forward a bit more.
I've a couple of weeks before I can get the rig indoors I'd like to try and sort a freestanding chrono too for the rig asap. Will be very useful. The steel base is also begging for a magnetic dial gauge of sorts so might give us an indication of barrel vibration.

There's one thing that I have noticed though and ofcourse it's quite important in my game.. I can zero the 9015 in the clamp rig and when I refit the action into the modified chassis, there's absolutely no discernable shift.

I just wish my hand was in a better state as I've got a few test stocks I need to try out,but can't safely use the tooling right now☹️
 
BallisticBill said:
Some light reading for anyone who can't get to sleep. 😜
Click to expand...
Well, mine should definitely help insomnia sufferers.

On bullets having tighter groups at long range than at short range, it is, as said earlier, due to bullets reducing yaw i.e. going to sleep, as they fly down range. The reducing yaw reduces the heave and swerve of the bullet. That is all very well, but not all bullets are dynamically stable, I have even seen film of the same bullet make being fired from the same rifle where some reduce yaw but some just keep it as it is. Pellets unfortunately appear to be dynamically unstable, so the yaw increases as they move down range, which is probably the cause of spiralling.
 
You must log in or register to reply here.
Back
Top