Using Quick Load for Optimum Barrel Timing and OCW Node Matches

[Veteran]

It's hard for me to believe it could work.
For one, 'optimum barrel time' seems a misnomer. You're really theoretically identifying 'terrible barrel times'. Right?
That is, the points where vibrations hit the muzzle. A condition where bore dimensions change, right at the muzzle, by a vibration wave.
But actual optimum barrel time remains unknown, as there are more than one type & source of vibrations and barrel movements, all interfering with each other, with some providing MV compensation.

Then optimum powder charge, or powder tune, is separate and different from barrel tune.
Neither is predicted with ANYTHING.

Mike, This is a several step process.

Running QL or GRT to get a bullet exit time for a given bullet and powder charge tells you nothing.

First you have to review the Chris Long paper and his theory on frequency and harmonic nodes.
His calculation is supposed to tell you at what time the bbl. is pointing consistently in the same direction.
You have to use his spreadsheet to calc. those OCW milliseconds, you then use GRT and or QL to find a bullet/powder combination that gives you a bullet exit timing that matches most closely with the Chris Long Harmonic Node bullet exit time when the barrel is consistently pointing in the same direction.

Haral's work using Finite Element Analysis is similar.

There are several steps, and several programs involved in these estimates.

They are not spot on, but in my experience get you close enough to save time and components.

But, its not something done with or by GRT or QL alone.

 

[K.E.C. Darkside]

Tag I'm in. I just bought and loaded QL.
I have a lot to learn. Thanks

 

[Mikecr]

After independent development and OBT correlations, my conclusion:
We believe what we want to believe

 

[Veteran]

After independent development and OBT correlations, my conclusion:
We believe what we want to believe

Yep, agreed. I dont believe Epstein hung himself or that Oswald was the lone ranger. Nor that our world, or government, institutions, or corporations are honest, transparent, and without corruption.

I generally have both eyes open, and each man has to see, and evaluate everything for themselves.

I still believe in Caveat Emptor too.
The whole world cannot be a victim.
Consider all, and believe what you will.

 

[Oak_Leaf]

I'm gonna just go ahead and say this because I see people making incorrect references to the different theories of harmonics and OBT all the time. Chris Long's OBT theory, and the harmonic bending modes are not the same thing.

The bending modes (harmonics) determine which way the barrel is pointed at a given time, and we use this to positively compensate our MV spreads over a charge range, at a specified distance. Chris Long's theory has to do with the wave that repeatedly expands and contracts the bore. These are two totally different beasts. Chris's theory really has to do with group size variations, in general, and has nothing to do with positive compensation that happens to the bending modes.

When you're looking at barrel times in QL, you will have both a bending mode (harmonic) AND a bore size change BOTH affecting the rifle - and each one could be favorable or unfavorable at that barrel time. For example, here's a common scenario ... say QL was accurate, and you found a load that 100% matched up to the Chris's OBT, you could also be at a unfavorable spot in the bending cycle. That load might shoot tiny groups, but poi would be sensitive to MV changes, like temperature or powder charge variations. A load like this, I believe, would be referred to by most shooters as "not in a node".

When people find their "node" - via OCW, ladder - what they've found is a sweet spot on the bending cycle that allows for good positive compensation over their MV spreads over that charge range. But, because of the way positive compensation works, it only compensates at that specific distance you worked up your load at - and you may or may not be at an OBT. In other words, a "node", as most of us refer to from the OCW or ladder test, is not very sensitive to MV changes and works well across temp changes, etc., but it may not give the tiniest groups because it may be not aligned with an optimum barrel time.

These two phenomenon are talked about all the time as if they are the same thing, and they are most definitely not. But, it makes for good long thread, lol.

ETA - but if you can find a recipe (rifle, powder, bullet, etc) where the bending modes AND the OBT are both favorable, and you have low MV spreads to top it off, then you got a real shooter. I believe a lot of the competition guys doing the high precision and ELR shooting have these recipes figured out.

 

[Mikecr]

In Rifle Accuracy Facts, Harold Vaughn identifies all kinds of things happening in our metal during bullet travel.
This leads to the barrel tune abstract, which has never been predictable.

Then you have powder tune, which is separate and different from barrel tune.
With this, you can find a forgiving charge with lowest ES/SD -that shoots like crap..
So barrel tune dominates.
The only way to put both tunes on top of each other is to use a barrel tuner.

Offensive vibrations along the way? Whatever they end up, targets & the chrono show them.

 

[Veteran]

Yep, I use bbl tuners. Love

In Rifle Accuracy Facts, Harold Vaughn identifies all kinds of things happening in our metal during bullet travel.
This leads to the barrel tune abstract, which has never been predictable.

Then you have powder tune, which is separate and different from barrel tune.
With this, you can find a forgiving charge with lowest ES/SD -that shoots like crap..
So barrel tune dominates.
The only way to put both tunes on top of each other is to use a barrel tuner.

Offensive vibrations along the way? Whatever they end up, targets & the chrono show them.

In Rifle Accuracy Facts, Harold Vaughn identifies all kinds of things happening in our metal during bullet travel.
This leads to the barrel tune abstract, which has never been predictable.

Then you have powder tune, which is separate and different from barrel tune.
With this, you can find a forgiving charge with lowest ES/SD -that shoots like crap..
So barrel tune dominates.
The only way to put both tunes on top of each other is to use a barrel tuner.

Offensive vibrations along the way? Whatever they end up, targets & the chrono show them.

Yep, I use bbl tuners. Big believer in them. Still try to optimize my loads too.

 

[Veteran]

I'm gonna just go ahead and say this because I see people making incorrect references to the different theories of harmonics and OBT all the time. Chris Long's OBT theory, and the harmonic bending modes are not the same thing.

The bending modes (harmonics) determine which way the barrel is pointed at a given time, and we use this to positively compensate our MV spreads over a charge range, at a specified distance. Chris Long's theory has to do with the wave that repeatedly expands and contracts the bore. These are two totally different beasts. Chris's theory really has to do with group size variations, in general, and has nothing to do with positive compensation that happens to the bending modes.

When you're looking at barrel times in QL, you will have both a bending mode (harmonic) AND a bore size change BOTH affecting the rifle - and each one could be favorable or unfavorable at that barrel time. For example, here's a common scenario ... say QL was accurate, and you found a load that 100% matched up to the Chris's OBT, you could also be at a unfavorable spot in the bending cycle. That load might shoot tiny groups, but poi would be sensitive to MV changes, like temperature or powder charge variations. A load like this, I believe, would be referred to by most shooters as "not in a node".

When people find their "node" - via OCW, ladder - what they've found is a sweet spot on the bending cycle that allows for good positive compensation over their MV spreads over that charge range. But, because of the way positive compensation works, it only compensates at that specific distance you worked up your load at - and you may or may not be at an OBT. In other words, a "node", as most of us refer to from the OCW or ladder test, is not very sensitive to MV changes and works well across temp changes, etc., but it may not give the tiniest groups because it may be not aligned with an optimum barrel time.

These two phenomenon are talked about all the time as if they are the same thing, and they are most definitely not. But, it makes for good long thread, lol.

ETA - but if you can find a recipe (rifle, powder, bullet, etc) where the bending modes AND the OBT are both favorable, and you have low MV spreads to top it off, then you got a real shooter. I believe a lot of the competition guys doing the high precision and ELR shooting have these recipes figured out.

The only way I know to model both the change in bore size due to pressure and sound waves, and the bending moments due to harmonics
all at the same time would be via Haral's Finite Element Analysis, with a Lawrence Livermore Lab model which cell by cell, and time step by time step models every infinitely small segment of the barrel as all of these forces are exerted on it.

So, using solely Chris Long's work doesnt get you the whole answer but it can start you in the right direction and get you close. As I said, in threads above, its not definitive but saves you time and components in your load development.

Not many of us nor none of us has an FEA model to do the comprehensive job which will be more definitive.

I do believe the shorter and fatter the bbl., the more accurate and definitive answer you will get using just the Chris Long method, where bending moments and harmonics are not as severe, and the main issues may be just pressure and sound wave bbl. expansion and contraction.

On the other hand, thin skinny longer length bbls. have to have the complete FEA analysis due to much more pronounced bending moments or bbl. whip ie harmonics.

So, Chris Long method may not work very well the longer and skinnier the barrel.

But, the barrel expansion/contraction due to pressure and sonic waves is a frequency harmonics or cyclical modulation as well. Its just different than the bending moment
harmonics that also result.

 

[Oak_Leaf]

First, if my post sounded terse, I apologize. It wasn't really geared toward you, but more toward another reference whose text that you had copied. That reference made it sound like OBT and harmonics were the same phenomenon. It happens a lot, even on the other site

But yes, you are correct in that Chris has the only reasonable way to come up with any kind of educated guess as to what barrel time might produce a sweet spot for the expansion/contraction modes. But, like another poster said, I too believe that the barrel bending mode is usually the dominate factor over the expansion/contraction of bore, even in heavy barrel rifles. And, I think it has been shown in the real world scenarios that nodes (bending cycle sweet spots) can be found in certain velocity ranges, for a given barrel length length. These velocities will likely correspond somewhat with a particular barrel time. Again, a loose correlation. But when you find those sweet spots through actual target ladder/ocw, then calibrate QL correctly to your velocities, then you could conceivably determine an actual barrel time that correlates with the bending modes. This barrel time can be somewhat portable over to a different load for that rifle. I have done that before on a several rifles changing powders, and even bullets, and believe it or not it works, but again the correlation is a little looser.

The problem I have with QL for this type of work is that I have never successfully calibrated it to my actual velocities and had that calibration hold up over any useful range of charges. There's the popular way of calibrating, using Burn Rate, Weighting Factor, etc., but it just doesn't hold up over a very wide charge range. My program inputs are all very exact too. I think the REAL calibration would involve getting into the other parameters of the powder, but I do not know enough about Julian's model to get into that yet. I have tried some things, and actually gotten it to track over a wide range, but I am pretty skeptical of what I had to do. This leaves me doubting any barrel time other than for the charge I specifically calibrated the velocity to - and honestly, I'm skeptical of that one too. At the end of the day, when I find a good load, what I'm seeing is the OBT, according to Chris's calculations, does not line up with the barrel time in QL for the charge, or charge range, that shoots the best. Again, I believe it is because the bending modes are the dominant. In my mind, that pretty much messes everything up for me because of the possibility that the OBT is getting masked by the bending modes, so true calibration of QL to Chris's predictions becomes almost impossible. Hope that makes sense.

 

[Veteran]

First, if my post sounded terse, I apologize. It wasn't really geared toward you, but more toward another reference whose text that you had copied. That reference made it sound like OBT and harmonics were the same phenomenon. It happens a lot, even on the other site

But yes, you are correct in that Chris has the only reasonable way to come up with any kind of educated guess as to what barrel time might produce a sweet spot for the expansion/contraction modes. But, like another poster said, I too believe that the barrel bending mode is usually the dominate factor over the expansion/contraction of bore, even in heavy barrel rifles. And, I think it has been shown in the real world scenarios that nodes (bending cycle sweet spots) can be found in certain velocity ranges, for a given barrel length length. These velocities will likely correspond somewhat with a particular barrel time. Again, a loose correlation. But when you find those sweet spots through actual target ladder/ocw, then calibrate QL correctly to your velocities, then you could conceivably determine an actual barrel time that correlates with the bending modes. This barrel time can be somewhat portable over to a different load for that rifle. I have done that before on a several rifles changing powders, and even bullets, and believe it or not it works, but again the correlation is a little looser.

The problem I have with QL for this type of work is that I have never successfully calibrated it to my actual velocities and had that calibration hold up over any useful range of charges. There's the popular way of calibrating, using Burn Rate, Weighting Factor, etc., but it just doesn't hold up over a very wide charge range. My program inputs are all very exact too. I think the REAL calibration would involve getting into the other parameters of the powder, but I do not know enough about Julian's model to get into that yet. I have tried some things, and actually gotten it to track over a wide range, but I am pretty skeptical of what I had to do. This leaves me doubting any barrel time other than for the charge I specifically calibrated the velocity to - and honestly, I'm skeptical of that one too. At the end of the day, when I find a good load, what I'm seeing is the OBT, according to Chris's calculations, does not line up with the barrel time in QL for the charge, or charge range, that shoots the best. Again, I believe it is because the bending modes are the dominant. In my mind, that pretty much messes everything up for me because of the possibility that the OBT is getting masked by the bending modes, so true calibration of QL to Chris's predictions becomes almost impossible. Hope that makes sense.

I would also like to point out that you cannot expect tuning QL to match velocity over a really wide range of charge weights by varying burn rate to work.

Burn rate is certainly not a linear curve with temperature as I have seen it go exponential.

I don't believe it is linear with pressure either.

So over a wide range of velocity and charge weights and for differing bullets, etc. its always gonna have to be recalibrated for the specific velocity and charge range you are in. Its a non linear function.
Just works on small segments of the curve at a time.