Ladders and OCW decipher

[jlow]

So back to the analysis of your OCW - this is how I do mine.

In the attached image is your OCW but analyzed by me using the OnTarget software (free). The useful thing about OT is it automatically calculates the average POI for your group. Because of the low resolution of the image, what I have also done is use a red arrow to point out the POI.


If you look at the POI starting from 42.6, you will see the POI sits slightly above the right top edge of the left "arm", as the charge weight increase, it moves a little to the right (42.9), then down into the left arm (43.2, 43.5), then at 43.8 it sits at a point a little to the left top part of the bottom arm. It stays there at 44.1, 44.4 and 44.7 before moving into the middle of the bottom arm at 45.


In OCW, this is what you should be looking for i.e. the POI not changing over a wide span of charge weight - that is your accuracy node that you should based your choice for a charge weigh to do seating depths with.

 

[Zero333]

My opinion is that you need to repeat the ladder test under better shooting shooting conditions while taking velocity readings on every single shot. It is also ok to shoot more than one shot at each load level, but still record the shot #, and velocity for each individual shot, so you have a complete set of data. Using powder weight only, makes the assumption that velocity produced will be proportional. Especially without having an optimized seating depth that is not necessarily going to be true. When you have the detailed data including the vertical POI for every single shot, and more you have the better, I highly recommend plotting it using Excel. It is really hard to interpret shots scattered all over a target. But, when you plot them on a graph it often becomes very clear. Excel has an X-Y scatter graph capability which lets you input velocity and elevation for every shot and then produces a graph. It can also draw a best fit line to make the results clearer. Here is an example, with three different bullets on one graph. They all produced quite similar results. I now target about 3420 fps for this gun in this bullet range regardless of powder used, and seating depth. My practice is to get the sweet spot velocity first, and then experiment with seating depth next. After that I change powder and primers trying to get velocity spread down. If you try to do it all at the same time, you end up with a dog's breakfast...

Thank you for explaining your method. I will reload the ladder and chrono it next time at the range which will not be till October 22nd. The graph you posted makes the whole idea so simple to understand !

 

[Zero333]

View attachment 991410 So back to the analysis of your OCW - this is how I do mine.

In the attached image is your OCW but analyzed by me using the OnTarget software (free). The useful thing about OT is it automatically calculates the average POI for your group. Because of the low resolution of the image, what I have also done is use a red arrow to point out the POI.


If you look at the POI starting from 42.6, you will see the POI sits slightly above the right top edge of the left "arm", as the charge weight increase, it moves a little to the right (42.9), then down into the left arm (43.2, 43.5), then at 43.8 it sits at a point a little to the left top part of the bottom arm. It stays there at 44.1, 44.4 and 44.7 before moving into the middle of the bottom arm at 45.


In OCW, this is what you should be looking for i.e. the POI not changing over a wide span of charge weight - that is your accuracy node that you should based your choice for a charge weigh to do seating depths with.

Thank you for taking the time to plot the POI on the OCW. I understand what you are saying clearly. I will redo the ladder in a week so I can chrono it, but at the same time I will test different seating depths with 44.4gr and see if I can tighten things up.

 

[jlow]

Thank you for taking the time to plot the POI on the OCW. I understand what you are saying clearly. I will redo the ladder in a week so I can chrono it, but at the same time I will test different seating depths with 44.4gr and see if I can tighten things up.

No sweat, testing seating depth is the next step but after that, depending on how much precision you are looking for, it might be worthwhile to come back and test the powder charge weight around the "best weight" thus far with the new optimized seating depth - after all, you have only tested at 0.3 grain intervals.

 

[RonAKA]

So back to the analysis of your OCW - this is how I do mine.

No sweat, testing seating depth is the next step but after that, depending on how much precision you are looking for, it might be worthwhile to come back and test the powder charge weight around the "best weight" thus far with the new optimized seating depth - after all, you have only tested at 0.3 grain intervals.

I agree with your method except for the averaging of three shots at each load. I will admit I have done that too, and that graph I posted, I believe was based on the average of three shots for each powder charge. I know why I did it, and I suspect your reasons are the same -- to average out inaccuracy.

However, the problem is that each of those three shots will have a different velocity. They are each telling a story about how velocity changes point of impact. If you don't measure velocity and don't include each of the three data points individually you are losing that story.

I am convinced the very best way to find out what the influence of velocity is on vertical POI, is to measure the velocity of each bullet individually as well as the vertical. Fine to shoot more than one with the same load, but don't average the results. Plot them individually and you will end up with a clearer picture of the real story.

 

[Doom]

44.7 is a known node and it appears you are near it, maybe at 44.6, and that will put the lower node at 43.5, which seems to agree with your results. The nodes are usually 3% apart and there's a scatter node in the middle, as you have at 44.1.

Work around those two nodes with seating depth and you should be good.

 

[jlow]

I agree with your method except for the averaging of three shots at each load. I will admit I have done that too, and that graph I posted, I believe was based on the average of three shots for each powder charge. I know why I did it, and I suspect your reasons are the same -- to average out inaccuracy.

However, the problem is that each of those three shots will have a different velocity. They are each telling a story about how velocity changes point of impact. If you don't measure velocity and don't include each of the three data points individually you are losing that story.

I am convinced the very best way to find out what the influence of velocity is on vertical POI, is to measure the velocity of each bullet individually as well as the vertical. Fine to shoot more than one with the same load, but don't average the results. Plot them individually and you will end up with a clearer picture of the real story.

RonAKA – the idea of using the average of three shots to determine POI is not my idea. This is part of the procedure designed by Dan Newberry who invented OCW. Check out this link and look at instruction #14.

http://optimalchargeweight.embarqspace.com/ocw-instructions/4529817134

 

[RonAKA]

RonAKA – the idea of using the average of three shots to determine POI is not my idea. This is part of the procedure designed by Dan Newberry who invented OCW. Check out this link and look at instruction #14.

http://optimalchargeweight.embarqspace.com/ocw-instructions/4529817134

I believe the "pseudoscience of OCW" is basically wrong. When you don't link velocity with every shot POI you are losing valuable data.

 

[Zero333]

44.7 is a known node and it appears you are near it, maybe at 44.6, and that will put the lower node at 43.5, which seems to agree with your results. The nodes are usually 3% apart and there's a scatter node in the middle, as you have at 44.1.

Work around those two nodes with seating depth and you should be good.

Thank you for your input and welcome to the forum.

 

[Zero333]

RonAKA – the idea of using the average of three shots to determine POI is not my idea. This is part of the procedure designed by Dan Newberry who invented OCW. Check out this link and look at instruction #14.

http://optimalchargeweight.embarqspace.com/ocw-instructions/4529817134

Thanks for keeping the thread going.

You and RonAKA are giving me lots to think about.

 

[jlow]

I believe the "pseudoscience of OCW" is basically wrong. When you don't link velocity with every shot POI you are losing valuable data.

Honestly I know Dan and he has my ultimate respect in terms of what he has done to help us shooter find accuracy nodes and it would be very difficult for me to say he is "wrong".... My experience and knowledge is nowhere close to that level.

 

[Doom]

I haven't had the pleasure of meeting Dan but do participate in the Practical Riflery forum. I have found the OCW method to work well. I seldom use the chronograph. When I do its after I have the approximate OCW tied down then try a range in the OCW range to fine tune it by looking at ES and SD.

Dan's method doesn't ignore the velocity of each shot, but it integrates velocity into the "system" which includes the barrel to produce an accurate round that tends to be insensitive to small changes in powder and primer lot, bullet weight, and brass variations.

 

[RonAKA]

I haven't had the pleasure of meeting Dan but do participate in the Practical Riflery forum. I have found the OCW method to work well. I seldom use the chronograph. When I do its after I have the approximate OCW tied down then try a range in the OCW range to fine tune it by looking at ES and SD.

Dan's method doesn't ignore the velocity of each shot, but it integrates velocity into the "system" which includes the barrel to produce an accurate round that tends to be insensitive to small changes in powder and primer lot, bullet weight, and brass variations.

I guess my method is more simplistic/basic and I like it because I understand it. No black magic involved. It is two basic steps:

1. Establish the sweet spot velocity for your gun by shooting rounds with varying velocity and plotting the vertical elevation vs velocity. Yes, you really do need a chronograph to do it well. But, you can try to substitute powder charge for velocity. It is a compromise because you are then assuming velocity is always proportional to powder charge. It generally is, but on a shot by shot basis, it quite often is not. In any case the purpose of this step is to identify a velocity band where velocity increases but vertical POI does not, or changes very little.

2. Step two is to develop a load that has a velocity spread (ES) that stays well within the velocity tolerant band identified in step one. The lower the ES the better. There are a lot of variables here, but most start with jump/jam, then move on to primer, powder type, and other things. What should be kept constant is the target velocity band. Somewhere in there should be your small groups.

Two things; identify velocity tolerant band, and then minimize your velocity deviation from shot to shot within that band.

 

[jlow]

I guess my method is more simplistic/basic and I like it because I understand it. No black magic involved. It is two basic steps:

1. Establish the sweet spot velocity for your gun by shooting rounds with varying velocity and plotting the vertical elevation vs velocity. Yes, you really do need a chronograph to do it well. But, you can try to substitute powder charge for velocity. It is a compromise because you are then assuming velocity is always proportional to powder charge. It generally is, but on a shot by shot basis, it quite often is not. In any case the purpose of this step is to identify a velocity band where velocity increases but vertical POI does not, or changes very little.

2. Step two is to develop a load that has a velocity spread (ES) that stays well within the velocity tolerant band identified in step one. The lower the ES the better. There are a lot of variables here, but most start with jump/jam, then move on to primer, powder type, and other things. What should be kept constant is the target velocity band. Somewhere in there should be your small groups.

Two things; identify velocity tolerant band, and then minimize your velocity deviation from shot to shot within that band.

I don’t think there is anything wrong to like one method over the other – it’s a free country after all.

What I find skeptical is people bad mouthing techniques that they have not even taken the time to read and understand.

 

[Doom]

I have to admit that with 64 year old eyes I hate ladders! It's hard to track shots at 300 yds. We should end up at the about the same answer with either method.

 

[RonAKA]

What I find skeptical is people bad mouthing techniques that they have not even taken the time to read and understand.

I read the OCW stuff and it makes no sense. Black magic is hard to understand. I'm a retired mechanical engineer who has expertise in the area of vibration analysis and and balancing. I can understand stuff that is science based. Black magic, not so much.

 

[Ned Ludd]

I read the OCW stuff and it makes no sense. Black magic is hard to understand. I'm a retired mechanical engineer who has expertise in the area of vibration analysis and and balancing. I can understand stuff that is science based. Black magic, not so much.

It's not "black magic". It's actually conceptually the same as a ladder test; looking for the effect of charge weight on POI. It's simply another method for load development aimed at finding a charge weight window within which minimalized effect on POI is observed. No more, no less.

 

[jlow]

I read the OCW stuff and it makes no sense. Black magic is hard to understand. I'm a retired mechanical engineer who has expertise in the area of vibration analysis and and balancing. I can understand stuff that is science based. Black magic, not so much.

Gstaylord is of course dead right – if you take the time to read up on the two methods, they are very similar. Both look for changes in POI as charge weight goes up and for a range of charge weight where there is no movement. Difference is OCW uses three rounds to get the POI where as Ladder uses one, the three rounds gives you a better idea of where the true POI is (kind of like why we use multiple rounds to figure out the true group size of our loaded cartridges, why more rounds is better than less…). One is shot at 100 yards, the other at 300 yards (or longer). The shorter range allows you to reduce the effect of wind and the longer range allows you to have more seperation. Other than that, there is no more black magic in one vs. the other.

Nothing says you should not use the MV information, I for one gets that info using my LabRadar for every shot I fire. Using every shot's MV like it is gospel is like using the POI of every shot and thinking it is the same. Although it is ideal to have every round loaded perfectly so that the only difference is charge weight, few if any can actually do this and so this is why multiple rounds and averaging is used...

Bad mouthing a method when you don’t take time to understand and then turning around and calling it black magic just makes you look bad….

 

[RonAKA]

Bad mouthing a method when you don’t take time to understand and then turning around and calling it black magic just makes you look bad….

This is an example of what I have trouble with, and categorize as "black magic":

"Engineer Chris Long's model of barrel
behavior suggests (simply put, and in part)
that the initial shock wave, generated by the powder
charge's ignition, travels at the speed of sound in
steel (about 18.000 fps) from the chamber to the muzzle, then back, in a repeated pattern. When this wave is present at the muzzle, there is
naturally much turbulence and obturation of the
"roundness" of the bore at the muzzle. However, when
this main shock wave has reverberated back to the
chamber end, the muzzle is relatively stable. This
window of opportunity, according to Chris, is the best
time for the bullet to exit the muzzle. The barrel is
basically straight, and relatively calm."

This is a totally different basis than the ladder method of determining where the sweet spot is.

 

[CharlieNC]

I've used all the methods mentioned above, and settled on a hybrid version for me. Bottom line is the nodes are the nodes and all methods will converge to the same answer, at least for a given distance. While it would be informative to see a more comprehensive study as Varmint Al and a few videos have shown across multiple barrels and charges, I have successfully used OBT enough times to be convinced that harmonic is a dominant contributor. This field seems to lack in publically available technology vs others such as the numerous advances in ballistics we are seeing these days.