Optimum barrel time: great theory or bunk?

[kthomas]

Why do they accuracy test when making loads for factory ammo?


You skipped the question about diffrent powder charges shooting to a diffrent POI.

Dont you think it's kind of ironic you have come to these conclusions based on your small samples. Vs millions of rounds fired in load development and competition fired by thouasands of people over the decades.

I think some guys have gotten way off in the weeds thinking not being able to decern the difference meaning there isn't one. And ignoring that it could be a resolution problem.

You speak as if there is one monolithic process to success with reloading. But there isn't. Every record setting BR shooter has a different reloading process. They all have their own conclusions on what works and what doesn't. This goes to @Rio Precision Gunwerks point a few posts above yours.

I'm not claiming for a second that I dispositively know what works and what doesn't. As reloaders we are all battling statistical relevance in our own testing procedures. Some people choose to accept that what conclusions we can draw from our sample sizes are extremely limiting, others choose to make more dispositive conclusions. Some recognize the extreme level of limitations we have in our testing (and thus, the limitations of conclusions we can make), and some operate on levels of hubris that's pretty typical of our species.

I've learned that the conclusions that I used to draw from one day of testing: whether it's a velocity "node", a specific bullet seating depth, charge weight per group size or ES/SD, neck tension tests versus precision and ES/SD, etc, may look really conclusive in one day of testing. Then I started to perform the same tests over two days, and the conclusions started to become much less conclusive. Then I started to do testing over multiple days and multiple conditions, and started to see that any so-called "nodes" aren't really nodes - they may have shot the best on any one given day, but over multiple days of shooting those "nodes" just start to disappear.

The only dispositive conclusion I've come to so far is that quality components and reloading gear matters. So does proper and consistent reloading technique. Holding tight tolerances on your reloads makes a MUCH bigger difference than trying to achieve some optimal powder charge.

FGMM has better precision and ES/SD than Hornady because they hold tighter tolerances. Not because they have found some magical powder charge through some black art process like OBT that happens to just magically shoot better in all different barrels and chambers across all different atmospheric conditions.

If anyone thinks the OBT process works (maybe it does), then I would suggest doing this - perform the exact same OBT test across 5 different days. Are the results repeatable? Does one (or maybe a couple) of charge weights show more precision than the others? Is this pattern repeatable across ALL 5 days? Do the best shooting powder charges on the first day continue to be the best shooting powder charges across the next 4 days? Do the worst shooting powder charges on the first day continue to be the worst shooting charges over the next 4 days of testing? If the results are consistent across all 5 days, then you may be on to something. If any of the results from one day are not repeatable on any of the other days, then perhaps it's time to re-examine the utility of such a test and what conclusions you can really draw from it.

 

[Huskydriver]

I stated clearly I was not arguing with Luddites.
My education is my own, and exceeds high school, back before they nerfed college entrance exams.
I take it you “don’t believe” in nodal effects in steel either? As I stated above, your belief or lack thereof is not a requirement of fact. The facts exist. You can research them for yourself or just ignore them, as is the want of so many these days who ignore facts in the face of their “belief”.
Because your pickup won’t run does not invalidate the science behind internal combustion. If you believe it does, that’s your problem.
LoL

First of all: I am the OP. I posted the question, great theory or bunk. You know: The fact of vibrational nodes isnt in question for those with half a brain or the ability to use google.
The question is whether we can predict them given the complexity of the effect, the science, and the math involved. I am using GRT and will be running some tests, but have never used it before. I am getting really tired of idiots. It seems the number of believers in Idiocracy increase every year.
The number of people denying established science is disgusting. I might as well join a flat earth society group to argue with them. I have plotted course and location with a sextant but that matters not to the idiots who “believe” the earth is flat. No amount of science will change their mind. The number of people with similar philosophies is increasing yearly.
Believe stuff or not, I don’t care. I retract the question. Go live under your rock.

https://www.sciencedirect.com/science/article/pii/S2214509522002467

 

[kthomas]

I think the OP, @Bbracken667, should perform the exact same OBT test over multiple days, if they are truly curious in the methodology and its usefulness.

If the results are consistent and repeatable over 5 days of testing, perhaps its on to something. If there is any variation in the results from day to day - then there's your answer right there. Can the conclusions made from the first day of testing be made after day 2? 3? 4? 5?

Edit to add:

I recommend this process for anything. Bullet depth test. Neck Tension. Primer seating depth. Annealing settings. Powder charge. Etc. Are the conclusions that you are drawing from one day of testing repeatable over multiple days of testing?

 

[secondofangle2]

As promised. Load development complete. Shots 7 through 12 and done. Brand new barrel with completely different specs compared to my last barrel. How did I do it this quickly? What is my method?

I know that a 390 A tip in a 375 cheytac likes to be pushed around 2900 ft./s with either H50 BMG or reloader 50.

And it likes that no matter how my barrels a waving or a Groovin or a swinging or a pulsing or whatever it’s doing.

 

[kthomas]

^ Magic

 

[secondofangle2]

Should I name my method after myself or some physics principal? Will that make it more convincing lol.

 

[Rio Precision Gunworks]

Should I name my method after myself or some physics principal? Will that make it more convincing lol.

My vote is for "Optimal Quantum Entanglement Sinusoidal Wave Charge Method."

Really want to drive home that your education exceeds high school.

 

[supercorndogs]

You speak as if there is one monolithic process to success with reloading. But there isn't. Every record setting BR shooter has a different reloading process. They all have their own conclusions on what works and what doesn't. This goes to @Rio Precision Gunwerks point a few posts above yours.

I'm not claiming for a second that I dispositively know what works and what doesn't. As reloaders we are all battling statistical relevance in our own testing procedures. Some people choose to accept that what conclusions we can draw from our sample sizes are extremely limiting, others choose to make more dispositive conclusions. Some recognize the extreme level of limitations we have in our testing (and thus, the limitations of conclusions we can make), and some operate on levels of hubris that's pretty typical of our species.

I've learned that the conclusions that I used to draw from one day of testing: whether it's a velocity "node", a specific bullet seating depth, charge weight per group size or ES/SD, neck tension tests versus precision and ES/SD, etc, may look really conclusive in one day of testing. Then I started to perform the same tests over two days, and the conclusions started to become much less conclusive. Then I started to do testing over multiple days and multiple conditions, and started to see that any so-called "nodes" aren't really nodes - they may have shot the best on any one given day, but over multiple days of shooting those "nodes" just start to disappear.

The only dispositive conclusion I've come to so far is that quality components and reloading gear matters. So does proper and consistent reloading technique. Holding tight tolerances on your reloads makes a MUCH bigger difference than trying to achieve some optimal powder charge.

FGMM has better precision and ES/SD than Hornady because they hold tighter tolerances. Not because they have found some magical powder charge through some black art process like OBT that happens to just magically shoot better in all different barrels and chambers across all different atmospheric conditions.

If anyone thinks the OBT process works (maybe it does), then I would suggest doing this - perform the exact same OBT test across 5 different days. Are the results repeatable? Does one (or maybe a couple) of charge weights show more precision than the others? Is this pattern repeatable across ALL 5 days? Do the best shooting powder charges on the first day continue to be the best shooting powder charges across the next 4 days? Do the worst shooting powder charges on the first day continue to be the worst shooting charges over the next 4 days of testing? If the results are consistent across all 5 days, then you may be on to something. If any of the results from one day are not repeatable on any of the other days, then perhaps it's time to re-examine the utility of such a test and what conclusions you can really draw from it.

Hornady used to run about the same SD as FGMM.

What tolerance do you think they changed? What tolerance does FGMM hold better?

 

[secondofangle2]

I’m going with “Barrel Uniform Logarithmic String theory High Impact Tuning”

The BULSHIT method

 

[kthomas]

Hornady used to run about the same SD as FGMM.

What tolerance do you think they changed? What tolerance does FGMM hold better?

I've never had Hornady ammo that had SD close to FGMM.

SD of FGMM for me has been around 6-7 fps. Hornady is about 20+. Through various years of manufacture and lots.

I would need specific information in order to answer such a specific question, at this point any answer I would give would be pure speculation. If one was to tour both ammunition facilities and obtained detailed insights into the processes and tolerances for each company, the answer would probably be pretty clear to that question.

 

[blue_ridge]

Just to dig this back up, because it’s an interesting concept. I’m skeptical because if your trying to predict which loads will perform best based on optimal barrel time, then doesn’t it all go out the window the moment that the temperature increases or decreases, thus changing chamber pressure and speed? And any significant elevation or DA changes? Not to mention primer, bullet, powder lot variations. New brass vs 1x fired etc.

 

[kthomas]

Just to dig this back up, because it’s an interesting concept. I’m skeptical because if your trying to predict which loads will perform best based on optimal barrel time, then doesn’t it all go out the window the moment that the temperature increases or decreases, thus changing chamber pressure and speed? And any significant elevation or DA changes? Not to mention primer, bullet, powder lot variations. New brass vs 1x fired etc.

If people went and tested a bunch of different loads on day 'A' and then went and performed the exact same test(s) on days 'B', 'C', 'D', etc., I would guarantee the conclusions from each day as to what's the "best" load would differ.

 

[blue_ridge]

What got me thinking about this again is the Little Crow Gunworks videos - exhaustive reloading explanation across 16 or 17 videos. Most of his instructions are based on fairly up to date wisdom for anyone who follows precision reloading practices fairly closely the last 10 years. FL size everything, common sense powder selection, buy enough components for the barrel life, etc. But he does test seating depth and feels it makes a noticeable difference. He also uses GRT OBT and says it helps him narrow down the search for the best loads. While I think it is mostly impractical, I could see there being some usefulness in narrowing down your load development process to loads within a certain window. Kind of like a more detailed version of - relying on crowd wisdom that 6 Dashers, Lapua brass w 105 hybrids and Varget XX.X charge weight works most of the time. Not relying on it from day to day, location to location, but simply using it to lower the amount of load development needed to get to a decent result. But FIIK.

 

[straightshooter1]

I've found that OBT helps me get into a small ball park faster. It doesn't tell me exactly what load works best, but it's a starting point to minimize the amount of time and expenditure of components to get there. I've also found it especially helpful when I get a new lot of the same powder that performs differently from my good old load, where I'll run a velocity test and then adjust the powder load accordingly to the OBT I had for the previous lot of the powder.

 

[Doom]

Just to dig this back up, because it’s an interesting concept. I’m skeptical because if your trying to predict which loads will perform best based on optimal barrel time, then doesn’t it all go out the window the moment that the temperature increases or decreases, thus changing chamber pressure and speed? And any significant elevation or DA changes? Not to mention primer, bullet, powder lot variations. New brass vs 1x fired etc.

The barrel velocity in the vibration cycle changes in the horizontal and vertical dimension so that there are periods where the barrel is moving slowly as opposed to periods when it is moving fast. This is the theory behind harmonics and vibrations such as node 1. In Chris Longs theory it's about the wave being away from the muzzle. In both cases these concepts create wide nodes. I would recommend you read :

http://the-long-family.com/OBT_paper.htm

 

[secondofangle2]

Wouldn’t OBT be ruled out if 2 barrels of significantly different lengths shot the same load well? Say 16” & 32”?

 

[supercorndogs]

No.

 

[blue_ridge]

The barrel velocity in the vibration cycle changes in the horizontal and vertical dimension so that there are periods where the barrel is moving slowly as opposed to periods when it is moving fast. This is the theory behind harmonics and vibrations such as node 1. In Chris Longs theory it's about the wave being away from the muzzle. In both cases these concepts create wide nodes. I would recommend you read :

http://the-long-family.com/OBT_paper.htm

I’ve read it and I get the theory, but I’m not sure it is practical. Do the harmonics work tomorrow the same as today?
1. Doesn’t barrel time change from lot to lot of powders?
2. How are you supposed to depend on Quick Load or GRT to predict the barrel time in your rifle? I’ve heard of people that had two identical barrels, made with the same reamer and same gunsmith, on the same action and they liked completely different loads.
3. What about ambient temp? Your barrel time is gonna change constantly.
4. Has anyone tested OBT in decent sample sizes against control loads? Across different weather conditions, altitude, elevation etc.

I just have a hard time believing OBT is practical or predictable when there are so many variables like powder lots, temperature, barrel variations, chamber variations, primers, bullets, brass, neck tension, elevation. Suppressors, etc. I think if OBT is to be used as a practical solution it would need to be in a very controlled environment with as few variables as possible. Short range Benchrest maybe or in a tunnel range.

 

[supercorndogs]

I think every question you are posing has been discussed at length in this thread.

 

[blue_ridge]

Just watched the Chris Long episode w/Eric Cortina, Believe the Target. From the horse’s mouth:

“Ok I’ll just say flat out OBT is a mechanical theory with some empirical data based ona software model that you can’t control. To me, it just gives you a starting point. It gives you a frame of reference to say maybe somewhere in here, this is about where I should start looking.”

Anyone trying to take it a step further and use OBT as a load development method or shortcut is just pissin’ in the wind.

 

[Doom]

I’ve read it and I get the theory, but I’m not sure it is practical. Do the harmonics work tomorrow the same as today?
1. Doesn’t barrel time change from lot to lot of powders?
2. How are you supposed to depend on Quick Load or GRT to predict the barrel time in your rifle? I’ve heard of people that had two identical barrels, made with the same reamer and same gunsmith, on the same action and they liked completely different loads.
3. What about ambient temp? Your barrel time is gonna change constantly.
4. Has anyone tested OBT in decent sample sizes against control loads? Across different weather conditions, altitude, elevation etc.

I just have a hard time believing OBT is practical or predictable when there are so many variables like powder lots, temperature, barrel variations, chamber variations, primers, bullets, brass, neck tension, elevation. Suppressors, etc. I think if OBT is to be used as a practical solution it would need to be in a very controlled environment with as few variables as possible. Short range Benchrest maybe or in a tunnel range.

Regardless of the development process that we as reloaders undertake there are some things that are never consistent. Between different shooters there are differences in ability and and shot to shot variations in the shooter's setup and the rifles themselves are different. Within a givern shooter there are inherent differences shot to shot because everything is different. And the evaluation is done by different observers in every case. The result is that even day to day testing can lead to idifferent and/or incorrect conclusions.

I don't know if Chis Long is right or not. The theory makes sense in general. Unfortunately it is difficult to test and it takes multiple test by multiple shooter to prove. What has been the case since the theory came out is there is a lot of anecdotal evidence that that OBT seems to predict where accurate nodes tend to be found. It doesn't prove the theory but it does give a place to start.

Dan Newberry in his OCW method was looking for why some ammunition shot well over a large sample of firearms with different barrel lengths. He actually used Audette's ladder concept with multiple shots and took the environmental out of the equation by shooting at 100yds isolating effects to the rifle and shooter. He found that there were loads that tended to have similar points of impact at differing charge weights (~ +/- 0.3 gn in a 308). For those of us who use this method one of the things that experience teaches is that often the most information is gleaned not from the good POI data but from the one where the the POI moves and the Group blows up. What we call the scatter node. What we see is the scatter node and good nodes seem to follow the patterns that the OBT theory predicts in QL and GRT.

As far as OCW working and being tested I can give you one example. IN 308 Winchester with the 168 MatchKing the with IMR 4064 almost everyone that does this test ends up with a load between 43 an 43.5 grains depending on the case volume (Win tends toward 43.5 and FC/Lapua/LC tends towards 43-43.2). This node it often chosen for case life. Both Varget and RL15 also fall in that range. This isn't the highest node which is about 1.0 to 1.2 gn higher. This is a well known and proven load. My load of choice is 43.2 gn at 2520 fps. GRT predicts the load at 2532 fps with a barrel time of 1.0693 ms and an OBT of 1.0684 ms. It is of interest that GRT calls this node 5-1/2. I do not know the details of this.

One word of caution, OCW and OBT do not guarantee that any particular load is going to yield the smallest group. It only attempts to minimize the variations in POI due to variations in charge weight/muzzle velocity (Barrel Time) and variations in the clearance between the bullet and bore at the muzzle.

 

[John Glidewell]

My load of choice is 43.2 gn at 2520 fps. GRT predicts the load at 2532 fps with a barrel time of 1.0693 ms and an OBT of 1.0684 ms. It is of interest that GRT calls this node 5-1/2. I do not know the details of this.

True your burn rate in gtr to match what your rifle is actually doing and see if the obt #s line up better. I posted a link to the obt calculator on page 1. Put .5 in the node block, that is how you find the barrel time for the .5 nodes. They are either a whole number or on the .5 number. If you know how to true a profile with actual and correct data, the barrel times line up very close. Been doing this for years. Also do it for customers that need help with load development. If you know how to get and input correct data in quick load, it works. The real issue is most folks don't input good data and / or do not have good / consistent reloading process.

 

[Doom]

I used OCW for years before looking at GRT and one of the things that drove me crazy was finding the low 43ish 308 load and then finding a load at 43.8gn which didn't make sense because it should have been a scatter node. When I started using GRT I decided to test my OCW loads and model the results of the 43.2gn load and trued the model. Out popped the 5-1/2 node and then the model produced another #5-1/2 node at 43.8.

Supposedly the half node concept was put forward by Gordan and another one of the GRT team in response to people seeing results similar to mine.

 

[John Glidewell]

Supposedly the half node concept was put forward by Gordan and another one of the GRT team in response to people seeing results similar to mine.

It was actually mentioned in the White paper with the link to barrel time calculator. They said don't be afraid to play with decimals. Through years of doing this we found the .5 nodes tend to line up better in the 1.5 to 2 grains off max numbers. Bryan Litz told us he finds safe max and shoots from 2.5 to 1.5 off max and something shines. We have done both methods and running over the obt just makes load development easy. But you have to have good data in the system. I tell folks it is a bs in bs out software, so don't plug in bs data. It works if you know how to use it. We have done load development this way for years now.