Load tune vs barrel tune

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williada
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Re: Load tune vs barrel tune

#16 Postby williada » Sat Oct 22, 2016 12:43 pm

Graham, an excellent shoot and nearly all in the basket with great elevation at the target distance of 1000 yards. It is description of how the rifle performed at 300 where a positive barrel can be tight, and as you move towards the middle distances, it opens up, that is important; and then closes down at the longs, which indicates it is a positive barrel. That description is better than just looking at your one group at 1000 yards where the elevation spread is SFA just as you have observed. The 1000 yard group is confirming the barrel positive compensation profile at those velocities. Because the shots are all coming together at 1000 yards it is not the distance to examine the fall of slow and faster shots. The mid distance is, and that why I test for spread at 500 yards having done preliminary work at 140 yards with load development. You will soon know if you have a good neutral barrel or a good positive one. You don’t want a negative one.

It is important that you mentioned your drop in charge when it began to sing. Irrespective of how your gear suffered with a higher charge the issue was the velocity spread matched the compensating distance as I have talked about. That would enable the rifle to deal with small variations of velocity due to environmental factors too or the odd crook primer or bumping a kernel or two out when you reload and have not noticed.

If you just took the 1000 yard shoot in isolation a well tuned neural barrel, tight SD’s etc can perform well too, but the odd shot due to primers tends to go at 6 o’clock at 1000 yards whereas you poked one a little higher. It’s all about centring your group to maximise your score knowing what your barrel will do.

With regards Keith’s comments, they apply pretty much until your reach the longs. That 1000 yards is so hard to pin. May I say with greatest respect, the statement that,”the correct node is never the high one” is not really a golden rule IMO for a few reasons.

Firstly, it depends on what the barrel compensation profile is. If the barrel is positively compensating, the tune is set before the peak node and may run into the node a on a barrel upswing and after the trough on a barrel downswing and may fall back to the trough node. In both situations the barrel is rising, unlike a node tune where shots can exit on the crest or trough of the sine wave. The actual load has to be set within a velocity range timed to barrel lift which will allow it to compensate. A barrel weight can also be used to time the lift with bullet exit. In this scenario the weight is separate from weight designed to control torque if it is behind the muzzle. Its primary function is separate from a tuner forward of the muzzle to adjust harmonic length. That is separate from neoprene washers which dampen reflected vibrations and separate from a tuner forward of the muzzle which dampens reflected vibrations too - although, if you know what you are doing you can combine the lot. But the charge weight and corresponding velocity is the key factor. In this case, an upper node or a lower node may be chosen as a base for the compensation depending depending how the velocity spread works at the compensation distance you are trying to achieve.

Secondly, if the muzzle is being distorted from reflected vibrations or if it is a short stiff barrel, then we tend to tune on secondary, tertiary nodes because the primary cycle for the major node tends to be incomplete. You would need a much longer barrel or you could cut it back a very long way to find a peak or a trough. In this situation, it is easier to rely on stiffness to reduce oscillation rather than a true harmonic tune. At long distance you may have insufficient velocity to deal with the aerodynamic forces that apply past the overturning point of the projectile, as per the nodal pyramid I posted while back if you cut a barrel back too far. The emphasis with these barrels is an OCW tune rather than an harmonic nodal tune or a compensation tune. Sure we try to find the least distorted shape and load with very tight parameters and sneak up with tiny increments on seating depth to get results. These tunes tend to be in the middle of flat sections like a neutral barrel and not on a peak or a trough of a real harmonic node. Yes, many barrels can be neutral and a node can be found. We can distinguish between a barrel, with or without obvious nodes by examining the group patterns. We tend to pick that up on group shape at a small crest or trough rather than a string of flatter, similar sized groups with the OCW tune which may be fairly good where we tend to run with the middle group of the flat section to give us more room for changes in velocity should the temperature change for instance.

In the case of a negatively compensating barrel, when the bullets are exiting on the downswing i.e. before a trough or after a peak you need every bit of speed to hold elevation as distance increases. The golden rule was when you are getting vertical go harder.

Without repeating Alan’s analysis on velocity, I agree. There are plenty of people who burn steel, and screw brass to win.

In concluding, if you are a nodal tuner, have a closer review of the nodal pyramid which has been independently tested. It’s about finding the correct node for distance. Those experiments demonstrated the elliptical nature of groups at long range with winds over 10 mph and that at different node velocities, the axis of the group changes too. If you are serious about centring groups, you have to know what your barrel and load is doing particularly with an ellipse at long range rather than a round group. At the longs, the upper nodes were better performers in winds over 10 mph.

williada
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Re: Load tune vs barrel tune

#17 Postby williada » Sat Oct 22, 2016 5:52 pm

Thanks to the guys who we have worked with whose patterns are revealed below. They are representative of broad concepts not the detail. Chart C with further analysis has more to it which is not revealed at this point in time.

Image
Last edited by williada on Sun Oct 23, 2016 9:49 am, edited 1 time in total.

plumbs7
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Re: Load tune vs barrel tune

#18 Postby plumbs7 » Sat Oct 22, 2016 7:15 pm

Wow again my head hurts!
Ok macro positve tune- middle group row c
2 OCW neutral tune - row d extreme left , but have no velocity figures to be sure?
3 negative barrel tune-row b extreme right?
4 neutral tune suited to nodal tune-row C extreme right?
5 micro tune row B 51.2
6 extreme right upper and extreme left lower ?
7 negative
8 group e holds hope for 900 yds but need velocity figures?
9 I don't see anything that turns me on for 1000yds ?
10 row b ?

How did I go Sensai? I'm expecting bad ? #-o

williada
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Re: Load tune vs barrel tune

#19 Postby williada » Sat Oct 22, 2016 8:00 pm

Hint Graham, the dashed green lines show the macro trend or general barrel profile that relates to my previous diagram. These are examples of those barrel characteristics. Within the macro tune there are sections we can tap into for a micro tune like the area E if no standout position is recognised. Within in those micro areas we look at individual groups to explore with further testing. I dare not post how to map lower order vibrations to hone in on the best micro area and manipulate it.

williada
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Re: Load tune vs barrel tune

#20 Postby williada » Sun Oct 23, 2016 10:34 am

Some computer work and actuals. A couple of points, the general grouping characteristic holds over most distances. The application of tuners on different compensation profiles makes them difficult to use. Another reason why load development is done without a tuner first.

Mild positive compensation
Image

Simulated SD's on computer programs generally apply to neutral barrels because fast shots definitely go higher at long range compared to slower shots. If you have a negative barrel, slower shots go much lower than predicted SD's. Of course SD's really only apply where the shots are forming a normal statistical distribution. There are lots of reasons groups are skewed one way or another. The statistics should reflect what you have got to be meaningful and as such there is no substitute for real life testing.

Simulated SD’s
Image

Actuals
Image

Can you pick the group in the short range testing at 140 yards these actuals were using? Hint, look for a pattern in barrel profile C.

This was a neutral barrel with reflected vibrations during these tests. If you look closely for a section in the groups we chose the roundest group to minimise the distortion. It so happened this rounder group was forming a little higher than its mates either side. Its only subtle. But there is an element of the slightest positive compensation we can tap into if we load tight SD's. It compensated at 900. Tony repeated those 900 yard efforts in competition. Of course the initial charge tests were indicators to refine things. The barrel's underlying personality was a neutral barrel and so I did not expect it to hold at 1000 yards unless the crackers were perfect. It was also evident past that slight positive compensation point it would fall into negative compensation i.e.1000 yards.


Often one tune type can run into another. This can fool us into thinking we have a wide node when it ain't necessarily so.

The negative profile of barrel D in the 140 yard test found an area like "E" where there was a section of neutral barrel. I did not post the test of the different projectile but the barrel exhibited the same negative characteristic. The shooter was able to win the event but 1000 yards proved to be troublesome I was told. Again the simple charge tests do not reveal other refinements but are indicators of performance at different distances.

williada
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Re: Load tune vs barrel tune

#21 Postby williada » Sun Oct 23, 2016 4:54 pm

Just to up the ante

The estimated nodal peak lay between groups on the 140 yard test. So the actual very slight compensation point will lie just before the peak for fast pills in this case and run up to the top of the node for the slow pills. The actual groups will confirm how close we are. In reality the true point may lie at 875 yards with 900 being the upper limit.

This diagram also is posted to illustrate groups do repeat and temperature changes velocity. If we correlate that with a lesser charge, we can see where groups will form well before a node on a node and after a node. These change in velocities can be picked in the group patterns at 300 yards in the diagram to illustrate falling off a node. Those who use a variable tuner can quickly adapt to the change in velocity. But the key is to recognise the patterns which form at short range and realize there is something different cause your groups to change. Put your short range results on your ammo box and try to see what is happening at other distances.

Barrels with underlying neutral characteristics respond well to tuners. The tune windows are not very far apart on neutral barrels having found a key area because we are not focusing on fundamental lift but rather lower orders of vibration which tend to be subdivisions of the fundamental vibration, setting aside distortions.

I apologize if this is over the top. My dad always said, a bloke can have 40 years experience but don't be the bloke who has 40 times 1 year's experience. He won't learn much. Push the envelope.

Image

DannyS
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Re: Load tune vs barrel tune

#22 Postby DannyS » Sun Oct 23, 2016 6:29 pm

Great reading David, you're on a roll this weekend.

Cheers
Danny
You might as well be yourself, everyone else is already taken.

plumbs7
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Re: Load tune vs barrel tune

#23 Postby plumbs7 » Sun Oct 23, 2016 8:35 pm

When are you going to write a book ? Bryan Litz has nothing on you ! ( no offence Bryan! Still luv ya!)

williada
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Re: Load tune vs barrel tune

#24 Postby williada » Mon Oct 24, 2016 11:04 am

Greetings Danny, bloody cold and wet, can't shoot, no beer what else is a bloke to do if they are cabin bound. :D

Plumbs, I started but have had a few interruptions its a pain in the A...se. I have spoken to Craig and he will provide a spot at 7mm.com.au where test targets can be downloaded and from time to time when I get organised, I will put some other stuff up and answer the quiz at 7mm.com.au. Not that this site is not great but I am over PhotoBucket posting with all the tracking blah, blah and the bots on this site etc. Don't mind sharing stuff but with the right people who will put back in at a local level.

The biggest problem if I outline the full details and people do not really understand what they are looking for in specialist test procedures, they take their own shortcuts making results harder to achieve. The charge test alone is insufficient. It is better to give personal instruction in small groups than issue to many what they think are a set of theory papers. One slice of the pie at a time. There is so much to know to develop to a high level from armouring to load development even if you have been shooting a while that is different from short range competition.

It seems to me there are many smithing failures and reloading failures in the gear people shoot with. You should know what your rifle is doing and why at the top level. Otherwise you have to get through a lot of baggage at team practices and the people who are excellent shots with the right temperament don't make it because their gear or loads let them down. Prior preparation prevents piss poor performance. How many "P's" is that? Practices seemed to be filled with the gear checking rather than learning to work as a team to give the coaches the best opportunity with conditions to improve their skills too. So if we can collectively help one another before important matches then we can raise the bar and get a lot more satisfaction.

I wish to acknowledge Tony (Ecomeat), for his tireless application over a few years now, working through FO rifles and their improvement. My experience and research has mainly applied to .30 calibre. His ability to shoot well and provide the data has assisted me enormously to understand, and taught me a few things about 7mm. He has put back in at a local level where really the efforts to boost participation matter. =D>

plumbs7
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Re: Load tune vs barrel tune

#25 Postby plumbs7 » Mon Oct 24, 2016 1:39 pm

I'm just starting to get through ur last post.
David "Can you pick the group in the short range testing at 140 yards these actuals were using? Hint, look for a pattern in barrel profile C."

Row c second from the right?

Edit : yes I use to think what Tony was going on about was a waste of time. I've learnt heaps of things in development squad and my ( about to put the mocca on myself ) shooting has improved out of sight in the 10 months and has been a highlight of my shooting career. I've learnt easy 3-4 yrs of shooting in that time . We have a great little team and are imo just starting to Gell! Sad to see it coming to an end ! Most likely won't make it any further as there are Queens winners etc as long as ur arm. But have very much won with knowledge and experience thanks to a lot of good people ( including Tony) and especially threads like you have posted above !

At the last Nats nearly all of our team finished 5 th or better at the ton ( if I'm not mistaken?) with the other teamie not far behind! Which all a product of what we have learnt !
Again thanks David !

williada
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Re: Load tune vs barrel tune

#26 Postby williada » Mon Oct 24, 2016 8:41 pm

Correct Graham. Hope you progress with information supplied by Tony and Craig and others at the local level because that is the sport's future. David.

williada
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Re: Load tune vs barrel tune

#27 Postby williada » Mon Oct 24, 2016 10:08 pm

I have to make a comment about test procedures. It is highly desirable that the charge test has a minimum of 5 shots per group as the sample is dreadfully inadequate if there is less. I examine the whole spread which is closer to 30 shots for the barrel macro profile including prospective sections. I use further tests to confirm the prospective groups which add to their sample size. I would use more, but the trade off is barrel wear by the time you complete all tests to nail seating depth, ignition, barrel lift etc. assuming your rifle is armoured correctly. One swallow does not make a summer.

As we approach a tune area, the smaller sample will be more representative otherwise any small sample like a 3 shot group could be part of a random scatter and mislead you. We of course confirm the short range testing at selected distances .

The rotation of five shot groups in the series also allows me to track secondary, tertiary waves etc in advanced analysis (which a very few have been exposed to) over all the shots as one variable changes i.e. the charge.

I certainly do primer testing before charge testing.

Shooting less than 140 yards is not ideal because the bullet has not settled and is still coning around its trajectory axis. This can distort the interpretation of trends give false nodes and interfere with tracking different harmonic vibrations. At 140 yards wind and light effects are minimised.

The 140 yard tests also pick up armouring faults by way of fliers which can not be attributed to wind and reveal bounce and rifle balance.

In order to diagnose some of those things the incremental loads of the test are shot in round robin order with a set time delay to expose problem barrels with heat issues or fouling.

So that charge test is very important as it forms the base for further development and selection of a tune type most suitable for the barrel personality. Shortcuts here with process do not cut the mustard I am sorry to say. :wink:

Normmatzen
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Re: Load tune vs barrel tune

#28 Postby Normmatzen » Sat Dec 10, 2016 1:50 pm

I am very aware of Williader's work (and extremely impressed!) as well as a student of Graham Mitcham's book on Optimum barrel length.
I started characterizing barrels by shooting various loads in round robin fashion in five shot groups to find low ES. I have gone one step better by plotting the ES vs powder load in EXCEL and doing a curve fit and have found that a 2 to 5 power polynomial curve will connect all the ES points and actually give you accurate dips and peaks from which you can find the "real" load for lowest ES. Instead of cutting my barrel back, I put my tuner on and find a curve of tuner setting vs group size again using EXCEL.
I had a new 7mm barrel chambered a couple months ago and followed this regimen and ended up with a barrel that out-shot my previous 7mm barrel as well as matching the best 600 yd group I have shot to date in my 6BRX! I have since had two 6mm barrel freshly chambered in 6BRX and the first one to be characterized in this way appears to be a real shooter as well.
Strangely, as "everyone" determines a proper load then tweaks for best jump, I also tried shooting groups with different jumps once I found proper load by the above manner. Ironically, the best group was shot using the exact jump used in the test group used to find best ES! I have long suspected that adjusting jump is nothing more than fine tuning the load, this tends to support that theory. Using EXCEL and its curve fitting routine will find the best load including the jump used for testing. I could think of no physics related reason why a barrel "likes" only one jump. Changing the jump simply varies the case volume a tiny bit, which could be done by altering the powder charge by a few granules!
I shoot these characterization tests at 200 yd as that is far enough to give meaningful groups as well as being near enough to allow fewer shooter errors. I also do the initial tuner tuning at 200 yd which seems to work pretty well at 600 yd. 1000 yards is a different matter as proper compensation rears its ugly head so testing at 1000 yd is required to optimize that barrel at 1000.

I have grown very fond of the 0zfclass site as it contains more real test data than the web sites here in the USA where anecdotal evidence is the rule.
Norm

williada
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Re: Load tune vs barrel tune

#29 Postby williada » Mon Dec 12, 2016 4:30 pm

Yes, Norm the horizontal charge tests just show you so much. Maybe you have been in deeper discussion with Peter C. The electrical engineers really understand vibration analysis. Glad you have a handle on this stuff. I have tried to focus my discussions in the past on extreme spread and the use of Excel because most ballistic programs simply do not do it. This plays role at 1000 yards particularly trying to account for primer variation. Of course ultimate group size matters whatever combination or tuning method you use. We have been using polynomial trend analysis for many years too then linking this to tune applications.
The chamber and throat are the major part of the pressure vessel. Given we now have scales to accurately weigh powder charge to .001 of gram, that powder is the most significant factor. Most people in the past would adjust seating depth rather than be finicky about charge weight because they did not have the right tools. Old habits die hard. We know this is not a winning way these days. But sometimes we still have to fine tune with seating depth and sometimes neck tension to sneak up on more productive areas because the true node, which we are after as a baseline, and which these processes help find, is strictly velocity dependent. At other times a less than perfect barrel needs to find further cycles in the sine waves to take out pressure spikes. This is more a remedial situation.

Just to digress, to demonstrate the importance of seating depth, I remember a time when I was contacted from England to say they have changed the powder for the Bisley shoot from the stuff we did the testing with in Blue Box and Brown box. Because they were using issued ammunition my advice was to take the throat out an extra .015” with the throat reamer the armourer has. This was better than a guess because through method we knew how the rifle would perform. Those that did the job had a smile at the conclusion with top results e.g. Peter P.

If you use a pressure trace you can identify the significance of these things more accurately. There is however a problem with in bore yaw, particularly in sloppy throats using boat tailed bullets that adjusting seating depth can address.

We add tuners to the mix to control the 3rd point of inertia at the muzzle too, as the projectile emerges with higher frequencies generated there as opposed to the chamber with fundamental lift because we are substituting the tuner for powder/muzzle angle for velocity. This accounts for why small increments of variable tuners can work and if they are of sufficient weight - the torque, compensation and if forward of the muzzle, the reflected vibrations can be manipulated as well. It’s very complex to get the union right, but the paper tells the story and so does polynomial trend analysis when all data points are mapped as you have seen for yourself.

I still prefer to look at an incremental charge test to visually check for vibration trends because it is simple and quick and on the spot rather than dragging out the computer even though the polynomial curve fit identifies the starting point for further load development. For me, the low extreme spread represents an area where the barrel is straighter and the bullet is not impeded by a bend. It correlates very well with the best group size with the best muzzle position a barrel is capable of at that point in time.

The paper always tells the story when at times the chronograph is suspect. Never trusted chronographs and I use the visual to confirm. With the use of the Lab Radar greater certainty is possible. My incremental charge target has a grid to assist me with a number of different ballistic calculations that better tools are now capable of solving. But the groups always reflect the vibrations that formed them if you discount bum shots or conditions.

The important thing to know, that as you reach a tune the sample size does not have to be big because it should be representative of a true node with low ES. The polynomial or vibration analysis puts you in that place quickly. If shots are outside the limits of the best tune spot, something else is wrong with position or equipment.

To me the important thing is the trend analysis because it saves burning valuable steel. The trend analysis conducted with 5 shot groups over 6 powder increments is statistically significant and tells you so much as to whether a rifle requires remedial armouring or not, and allows for comparison if you want to do another charge test of primers, powders and projectiles. I happen to do primer testing while breaking in a barrel. It tells me enough. Peter S on the compensation thread has an effective quick way of verifying powder lots.

While pet loads can be used as starting points for the same case design which gives similar vibration signature, the evidence from trend analysis tells us barrels have distinct personalities. The old days when teams went away with strict specs for chambering by today’s standards could do with improvement on an individual outcome basis.

A team in the past went away with a different barrel profile to the test barrels. That would not happen today. Seen it all.

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macguru
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Re: Load tune vs barrel tune

#30 Postby macguru » Tue Dec 13, 2016 8:11 am

These curve fits look nice, but my advice would be the triple the number of plot points and see what happens to the curve shapes ....
id quod est


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