OCW - chrono?

[davere]

Going to be doing my first attempts at OCW shortly. I have a Magnetospeed Sporter - it doesn't seem to affect POI, but my groups seem to be larger with it on the gun. Dan Newbury doesn't mention anything about chrono'ing while doing an OCW work up, and the procedures don't really require knowing that piece of info to be effective. But, I see a lot of folks posting velocities with their OCW info. Given my change in group size (50-70% larger), should I be leaving the chrono off the gun for OCW testing, and then chrono the resulting best load... or run with the (potentially) larger groups and then just worry about absolute group size when I start tuning seat depth, etc?

 

[Sheldon N]

Last load development session I did the following.... load 5 rounds at each charge weight. Shoot 2 shot groups through the series with the chrono on to get velocity for each charge weight. Then remove chrono and shoot the remaining 3 shots per charge weight as a regular OCW test on a separate target without the chrono attached.

Go home and plot out the velocity curve from the 2 shot series in excel... look for flat spot in velocity vs charge weight. Compare that to the OCW test looking for similar POI on target. For me there was good alignment with the velocity flat spot as well as OCW point of impact. Upper node didn't show much promise for group size but lower node shot bugholes. Went with the lower node, called it good after some final testing to confirm.

I really dig adding the velocity curve to the traditional OCW test. It's very easy to do in Excel.

 

[spife7980]

Yes leave it off. Once you find what you believe to be your load chrono some of those and verify it isn't way out of whack. Well if you want paper results that is. Some people shoot them all with the chrono on and then plot that data and try to back into the recipe from the numbers. Ultimately they should agree with one another in the end.

Edit: or the best of both worlds and do both ^^^

 

[supercorndogs]

Last load development session I did the following.... load 5 rounds at each charge weight. Shoot 2 shot groups through the series with the chrono on to get velocity for each charge weight. Then remove chrono and shoot the remaining 3 shots per charge weight as a regular OCW test on a separate target without the chrono attached.

Go home and plot out the velocity curve from the 2 shot series in excel... look for flat spot in velocity vs charge weight. Compare that to the OCW test looking for similar POI on target. For me there was good alignment with the velocity flat spot as well as OCW point of impact. Upper node didn't show much promise for group size but lower node shot bugholes. Went with the lower node, called it good after some final testing to confirm.

I really dig adding the velocity curve to the traditional OCW test. It's very easy to do in Excel.

That is a pretty damn good idea.

 

[Juggerxxx]

I have preformed OCWs with and without the Magnetospeed on the barrel. My lighter barrels gave me conflicting results after loading up rounds biased on the OCW with the magnetospeed attached. My larger varmint barrels didn't seem to care one bit.

 

[CharlieNC]

One good reason to own the old optical chrono......

 

[morganlamprecht]

no need, leave it off...get your load done, chrono later

 

[Niles Coyote]

Or you can run three of each load over the chrono and watch the sd/es trend. Find where numbers get tight and explore there.

 

[davere]

Solid idea, Sheldon, thanks - compromise.

Charlie, I do have an optical chrono, but it's a bitch to set up for prone shooting. Although, it's one of the better optical models (CED Millenium 2 w/ IR screens), I also tend to question its accuracy, so I tend not to use it for rifle, right now...

 

[Niles Coyote]

Here is a better definition of what I have been doing which sounds a lot like what Sheldon is doing.

 

[Sheldon N]

Yes, I drew a lot from that video also. Good stuff. I just wanted to see my on-target results without the influence of a chrono. Makes me wish for a Labradar.

 

[samb300]

FWIW, I like to load 8 rounds at each load for my OCW. I shoot 4-shots for each group, then give the rifle a little time to cool, then shoot the remaining 4-shot loads over the Magnetospeed. I make sure each group is shot on a unique bullseye, and I mark which groups are with the magnetospeed. Then I end up with two sets of targets to compare so I can see if the MS has any effect on group size. I can also look at the velocity trend in Excel with "sort of" enough data points to see what's going on. I personally wouldn't shoot only 2 shots through the MS, that might just leave you scratching your head and wishing for more information.

My last barrel was a medium palma and I found the group size wasn't really affected, but my POI was up approximately 0.3mil relative to my zero. My new barrel is a heavy palma and exhibits the same trend, but only shifts the group up 0.1mils.

 

[CharlieNC]

Solid idea, Sheldon, thanks - compromise.

Charlie, I do have an optical chrono, but it's a bitch to set up for prone shooting. Although, it's one of the better optical models (CED Millenium 2 w/ IR screens), I also tend to question its accuracy, so I tend not to use it for rifle, right now...

I use large rubber bands to attach my chrono to a 2x6 board that I lay in front. Even given a good sd, looking for a chrono node is unreliable unless a decent number of shots is taken.

 

[Sheldon N]

To clarify, when I shoot two shots at each charge weight I'm only looking for average velocity, not standard deviation. I just want to plot out the velocity vs charge weight curve and see if there is any area where the velocity flattens out.

 

[CharlieNC]

To clarify, when I shoot two shots at each charge weight I'm only looking for average velocity, not standard deviation. I just want to plot out the velocity vs charge weight curve and see if there is any area where the velocity flattens out.

Sheldon the inherent SD affects the variability of the average as well, such that with fewer samples the average is also more variable. This variability is given as standard deviation of the average,
SD(Avg) = SD(Individuals) / Square Root.

For example if the SD for the individual shots is 10 and you measure 2 shots to calculate the average, then the variability expected for the average is:
SD(Avg) = 10 / Sqrt(2) = 7.1.

The confidence in that average is such that there is a 68% chance that the REAL average is within +/- 7.1 of what you measured. Depending on how close the charge weight intervals were and the associated change in velocity, you are likely to be misled with only 2 shots. Of course knowing the SD and how many shots are needed to obtain a reliable estimate for it is altogether another issue.

 

[Sheldon N]

Yes, data is not perfect for a "true" average but it's good enough for a trendline. When you incorporate the average across multiple two round groups at 0.3gr increments, and then add in the data from fine tune testing at smaller increments, and look at the OCW data on paper it all starts to paint a complete picture.

Here's what I ended up with from my last load development... Yes, I could have shot another 10 or 20 rounds to make each average more accurate but I think the end result would have been the same.

 

[CharlieNC]

Sometimes yes, sometimes no. If it matches the target node then its a nice collaborating factor.

 

[samb300]

Yes, data is not perfect for a "true" average but it's good enough for a trendline. When you incorporate the average across multiple two round groups at 0.3gr increments, and then add in the data from fine tune testing at smaller increments, and look at the OCW data on paper it all starts to paint a complete picture.

Here's what I ended up with from my last load development... Yes, I could have shot another 10 or 20 rounds to make each average more accurate but I think the end result would have been the same.

Sheldon N,

That's actually not a trendline, it is data points connected by a smooth line. That line doesn't mean anything; you actually have no idea what's really going on between each data point. It may help visualize things but it cannot be trusted as a way to predict velocity between points. That graph should be either data points alone, or you could show it as a bar graph.

And yes, two velocity values may give you what you're looking for, but what if one charge gives you an ES of 5fps between the two shots, while another charge gives you 40fps? How certain are you that either of the two charges is representing the true velocity of that given charge weight?

In the end, two shot strings gives you some information, so there's nothing wrong with that. But if you're using the OCW method in its pure form without recording velocity data, then why even bother with the two shot strings? Might as well run the OCW, find the optimum charge, then chrono it to confirm what the average velocity is with a larger set of data points.

 

[Sheldon N]

That's actually not a trendline, it is data points connected by a smooth line. That line doesn't mean anything; you actually have no idea what's really going on between each data point. It may help visualize things but it cannot be trusted as a way to predict velocity between points. That graph should be either data points alone, or you could show it as a bar graph.

My apologies if you find that my data "doesn't mean anything" and that I "actually have no idea what's really going on" with velocity across charge weights. I would beg to differ with you, but rather than arguing with you about math I'll just let others decide if my approach adds any value to their process.

FWIW, the load I chose with this process had single digit SD, shot sub 1/2 MOA, and had identical 100 yard POI across a broad range of powder charge weights. Additionally, despite shooting a 308 178 BTHP at 2597fps I was able to pull out a 3rd place finish in Tactical Division and 16th overall out of 75 shooters in a 2 day field match with very windy conditions 2 weeks ago. I scored better at the long range stage which started at 1k yards than most of my squad mates shooting 6's and 6.5's.

 

[spife7980]

It may not mean much but I'm going to try doing it like Sheldon with a chrono just to see what the results say for myself. I imagine it will be helpful. I'm thinking I will do three or four shots per load and see how the first two compare to the second one or two. I bet it won't skew the results, just trim them up. It will be on an ms3 so I won't be looking at "ocw" info at all.

 

[samb300]

My apologies if you find that my data "doesn't mean anything" and that I "actually have no idea what's really going on" with velocity across charge weights. I would beg to differ with you, but rather than arguing with you about math I'll just let others decide if my approach adds any value to their process.

FWIW, the load I chose with this process had single digit SD, shot sub 1/2 MOA, and had identical 100 yard POI across a broad range of powder charge weights. Additionally, despite shooting a 308 178 BTHP at 2597fps I was able to pull out a 3rd place finish in Tactical Division and 16th overall out of 75 shooters in a 2 day field match with very windy conditions 2 weeks ago. I scored better at the long range stage which started at 1k yards than most of my squad mates shooting 6's and 6.5's.

Jeez dude, get defensive much?

I never once questioned the amazingness of your final load, or your extensive shooting accolades which you were so quick to point out.

From your data, can you tell me what the velocity is at a charge weight of 43.1gr? No, you can't. So using a smooth line to connect data points is a no-no in engineering land. I don't need to spout off why, since you clearly don't want to learn something when I wasn't even attacking you. I thought we were talking about data analysis; you thought we were debating your shooting skills.

SnipersHide is a great place because people can learn from each other. Clearly I can learn a thing or two about shooting from you because you're better than me (being serious, I won't claim that I am), but it should be a two way street. If you think you can't learn from someone else that may have an extensive background in engineering or data analysis then I guess I'll shut my mouth.

 

[CharlieNC]

Load development is an interesting combination of art and science, with a number of often debatable theories concerning methods and reasons (obt, ocw, ladder, harmonics, etc). In the end the target tells the story and if its good, whatever method works is fine. My latest load development was pure heresy whereby I changed charge and seating depth together (not one at a time) using 9 combinations x 2 shots each = 18 total shots for optimization.

 

[Sheldon N]

Jeez dude, get defensive much?

I never once questioned the amazingness of your final load, or your extensive shooting accolades which you were so quick to point out.

From your data, can you tell me what the velocity is at a charge weight of 43.1gr? No, you can't. So using a smooth line to connect data points is a no-no in engineering land. I don't need to spout off why, since you clearly don't want to learn something when I wasn't even attacking you. I thought we were talking about data analysis; you thought we were debating your shooting skills.

SnipersHide is a great place because people can learn from each other. Clearly I can learn a thing or two about shooting from you because you're better than me (being serious, I won't claim that I am), but it should be a two way street. If you think you can't learn from someone else that may have an extensive background in engineering or data analysis then I guess I'll shut my mouth.

What I'll point out is that when you use phrases like you did, you create an impression of denigrating others and it does come across as attacking. Secondarily going down the rabbit hole of trying to support data as a full empirically valid to the standards of the scientific method puts you in a place of having to burn a lot of rounds to get that data, often with questionable benefit.

My old method was simple - straight up OCW with no chrono attached to the barrel. Find a load. Chrono it when done. If the SD was single digit then good to go. The new method only added two rounds per charge weight and gave me more info and also helped validate the OCW results on paper. I'm not doing any math, just putting two columns of data in Excel and clicking "add chart". This is not meant to be a full data analysis... just answer the question of "What was my velocity doing when I was shooting that OCW?" and give me a bit of supplemental info. The old method had no chrono data so I wouldn't know if my max or min loads were fast or slow or whatever. This is just supplemental info that helps me interpret the OCW.

I don't want to run the 5 round ladder with chrono attached looking for both flat spot velocity node plus tightening SD's. I want to see results on paper with nothing attached to the gun. If I had a Labradar though this is the exact approach I would use so I can get both at once, but with a Magnetospeed that ends up with least 8 rounds per charge weight for the initial test... 5 for data and 3 for paper.

Yes, I understand stringent data analysis. Yes, I've taken statistics at both the undergraduate and graduate level. The thing is that I'm not here to do math or learn more about data analysis. I want to spend my range trips working on positional practice and getting better for competition rather than load development. You point out that my method is statistically invalid - that's fine because it was never meant to be a statistically valid test. I'm not here to brag about my shooting.. I'm not actually that good. I only brought up the match results to show that from a practical perspective my approach to load development worked well.

Finally going back to my point about the questionable benefit of chasing data....When you talk to world class 1000 yard bench rest shooters they will tell you not to chase the math or the lowest SD. They look at what load gives you the smallest amount of vertical at distance. They'll shoot a ladder or two with perhaps a dozen rounds to look for the "flat spot", then tune powder/seating depth for minimal vertical and smallest group size on paper at distance - SD be damned. I know of a couple world record holding shooters who would say that the lowest SD wasn't always the best load to choose.

 

[morganlamprecht]

if everyone could stop getting hung up on SD, it would save a lot of trouble and confusion

the SD for the amount of rounds we typically shoot in a string, it means literally dick...its just a nice reference value so people hang up on it

you shoot 2 rounds and they are 2500 and 2525....would look terrible...what if you shot 50 more rounds and they all fell in between? wouldnt be so bad then...and im not cutting down sheldon's methods, just using an example...i get what hes doin and i do similar when testing bullet/powder combos with little info out there...it does help, even if the data isnt perfect...it doesnt have to be

i cant count how many times ive shot 10 round strings and ill have 5 in there that are within 1-3 fps of each other, but the ES for the string is 20-25 fps...if chance would have had it, i shot those similar rounds in order, and stopped at 3 or 5, my numbers would look awesome and id be able to post a nice pic online

like sheldon mentioned, a low ES/SD doesnt mean an accurate load...ive seen it more than once
just the same, an accurate load doesnt mean low ES/SD (federal gmm 175s shoots ragged holes out of my AI, ES for 5-10 rounds is usually double any of my handloads)...as the distance increases, you do need a low ES to keep a handle on vertical though

and either im just lucky or for low ES/SD what matters, isnt where you load, but how you load and your barrel...i find an accurate load and then strap the chrono on, numbers for everything i load (for accuracy) are always similar...20-25 ES for 5-10 shots, SD 5-10, and i dont weight sort anything and dump with a chargemaster...223, 22 creed, 6comp, 6.5creed (multiple barrels), 308, 28 nosler

maybe one day ill see the pressure curve thing...or someone can show me...but it better be statistically meaningful, consistent, and repeatable...up until this point all ive seen are a few cherry picked examples of "one day i did this, the next day i did this...day 2 shot better so what i did different was the reason..." ...im not buying it

 

[samb300]

What I'll point out is that when you use phrases like you did, you create an impression of denigrating others and it does come across as attacking. Secondarily going down the rabbit hole of trying to support data as a full empirically valid to the standards of the scientific method puts you in a place of having to burn a lot of rounds to get that data, often with questionable benefit.

What I should have said was "That line doesn't mean anything; one actually has no idea what's really going on between each data point." You don't, I don't, no one knows exactly what is happening between two points. Clearly, saying the word "you" sent you into a defensive mode, where you even quoted me as saying I thought you didn't know what was going on (with velocity across charge weights)...when I was talking specifically about a curve between two points on a graph. It's a graph, it's data, it is what it is. That one sentence taken the wrong way was not intended to be inflammatory. I may disagree with the purpose and validity of 2-shot strings, but it's your barrel, ammo, time, money, etc., and I'm not going to change your methods anyway. You do an OCW and it works, well hell, so do I. I just burn up a few more rounds at each charge to get velocity data because 2 rounds would leave me questioning the data.

 

[morganlamprecht]

Once you get familiar with it all, you can chrono 1 round and take it to a match...just true it up on the fly lol really get people's blood pressure up

 

[Sheldon N]

What I should have said was "That line doesn't mean anything; one actually has no idea what's really going on between each data point." You don't, I don't, no one knows exactly what is happening between two points. Clearly, saying the word "you" sent you into a defensive mode, where you even quoted me as saying I thought you didn't know what was going on (with velocity across charge weights)...when I was talking specifically about a curve between two points on a graph. It's a graph, it's data, it is what it is. That one sentence taken the wrong way was not intended to be inflammatory. I may disagree with the purpose and validity of 2-shot strings, but it's your barrel, ammo, time, money, etc., and I'm not going to change your methods anyway. You do an OCW and it works, well hell, so do I. I just burn up a few more rounds at each charge to get velocity data because 2 rounds would leave me questioning the data.

Yes, your word choice certainly didn't help. The other issue that is at hand is your assertion that the data is meaningless because it is not as complete as you would like it. The trend line does mean something... it is an estimate of the path of intersection between charge weights and average velocity. That's a small but meaningful piece of info to have during load development. Yes, add another shot to each series and the line becomes more accurate. Make them 5 shots for each charge weight and it's more accurate still. Shoot 10 rounds at every charge weight at 0.1g intervals and the line becomes even more accurate. The question is how different is the line going to look from what I posted, and how many rounds are you willing to burn to perfect your data?

Your comment that "That line doesn't mean anything" and "one has no idea what's really going on between each data point" not only comes across as an attack, it's also wrong. What you could have said is "I'd personally feel better about the data if it was based on 3 shot strings" (or 5 or whatever). Instead you essentially said that what I did was worthless because it wasn't as precise as you would have made it. All I did was make a decision as to how many rounds I wanted to burn and what level of precision I needed and it worked for my purposes. If you feel better shooting more to have more accurate data then I don't disagree with that.

I'm not arguing that my way is better, just sharing something that I felt struck a good balance between providing helpful info and staying on the practical/efficient side of things.

 

[Sheldon N]

Once you get familiar with it all, you can chrono 1 round and take it to a match...just true it up on the fly lol really get people's blood pressure up

Hell, just skip chronoing all together and make corrections off the first miss. You can still win a match if you hit the other 9 rounds every stage.

Reminds me of a practice drill some friends showed me. Dial your dope and wind perfect, then turn your back and let your buddy spin both windage and elevation 0.5 in any direction and put a piece of tape over them so you can't see. Then you shoot, miss, and see how fast you can make the correction and get a second round impact.

 

[morganlamprecht]

Hell, just skip chronoing all together and make corrections off the first miss. You can still win a match if you hit the other 9 rounds every stage.

Reminds me of a practice drill some friends showed me. Dial your dope and wind perfect, then turn your back and let your buddy spin both windage and elevation 0.5 in any direction and put a piece of tape over them so you can't see. Then you shoot, miss, and see how fast you can make the correction and get a second round impact.

I like it!

 

[samb300]

Yes, your word choice certainly didn't help. The other issue that is at hand is your assertion that the data is meaningless because it is not as complete as you would like it. The trend line does mean something... it is an estimate of the path of intersection between charge weights and average velocity. That's a small but meaningful piece of info to have during load development. Yes, add another shot to each series and the line becomes more accurate. Make them 5 shots for each charge weight and it's more accurate still. Shoot 10 rounds at every charge weight at 0.1g intervals and the line becomes even more accurate. The question is how different is the line going to look from what I posted, and how many rounds are you willing to burn to perfect your data?

Your comment that "That line doesn't mean anything" and "one has no idea what's really going on between each data point" not only comes across as an attack, it's also wrong. What you could have said is "I'd personally feel better about the data if it was based on 3 shot strings" (or 5 or whatever). Instead you essentially said that what I did was worthless because it wasn't as precise as you would have made it. All I did was make a decision as to how many rounds I wanted to burn and what level of precision I needed and it worked for my purposes. If you feel better shooting more to have more accurate data then I don't disagree with that.

I'm not arguing that my way is better, just sharing something that I felt struck a good balance between providing helpful info and staying on the practical/efficient side of things.

Nope, never said the data was meaningless, I said the line was. Which it is. It's a spline that connects the dots, not a trendline that gives you an equation. It's simply a visual aid.

And I'm not attacking you when I said you don't know what's going on between each data point, it's a fact...because you don't. If you go out and shoot 43.0gr and 43.1gr and those two two-shot averages fall right on that spline, I'd be shocked. I'll admit it's possible, but I'd bet against it.

At this point let's just agree to disagree. You won't answer with any more data because there isn't any, and we both already know you're a better shooter than me (PRS scores) and smarter than me (you took stats in grad school).

 

[Sheldon N]

LOL I won't claim to be smart since I got sucked into arguing about math which I said I didn't want to do. And I won't claim to be good until I can actually hang with any of the legit PRS shooters in my neck of the woods. Shooting alongside them has only shown me that I've got a long way to go.

Not mad at you either, just killing time on a forum rather than finishing up all the work that's sitting on my desk on a Friday afternoon. And what better way than arguing about who's right and wrong on the internet?

Cheers, and have a great weekend!

 

[samb300]

Hey man, no hard feelings. I let my nerd rage get the best of me sometimes!

I will actually be shooting an OCW out of my new AX this weekend, so hopefully I will have something good to share. If it's anything like my last 6.5x47L it should be a pretty easy load development.

 

[lash]

Interesting to read the...uhm...discussion and while I agree that the line has no mathematical merit, it does serve the purpose that Sheldon is intending IMO. Yes, I'm also an engineer, but being in the practical application side of manufacturing, when I look at his "graph" I see essentially the same results as I would see if those same rounds were fired at 300+ yards in a ladder test.

I sure agree that points shot between those recorded would likely not end up on his "trend line", that is exactly what one would expect from a ladder test. What one is looking for is a spot where the loads hang together, giving you a node to work with. It's essentially just another piece of information to help nail down your load. Similar to what people use scatter diagrams/charts for when needing additional input before making a decision.

I get it and like it. May even use it for a load development in the future.

 

[davere]

I'd seen the 6.5 Guys stuff, and the Accuracy Tech stuff - seems like there's a few ways to skin the cat, and a pretty fair amount of opinion as to which is best. The "chrono only" method has its appeal - I'm pretty new to rifle shooting and that method pretty much eliminates the shooter from the evaluation. Part of me doesn't believe it if I don't see it on paper, too.

slightly off topic - when guys talk about letting the barrel cool for any of these tests... how cool is "cool"? Returning all the way to cold bore? Seems like a lot of standing around, if that's the case?

 

[samb300]

I think it might depend on your barrel contour. Light Palma heats up fast but cools fast, whereas an MTU would heat up slow but take longer to cool down once it's hot...etc.

You could do a test on your barrel and shoot a long string (say 20 rounds) and see if groups start to open up or wander.

Personally I don't worry about it unless it's really hot outside, or I shoot rapidly enough to not be able to touch the barrel. Once it gets to that point I may let it cool down for 10 or 15 minutes. And when I'm doing so I'm probably shooting another gun in the meantime

 

[morganlamprecht]

for most of my heavier match barrels, just 30 seconds to 1 minute between shots, just enough time so the barrel stays warm but isnt scorching hot...it doesnt have to be all the way cool

 

[davere]

Roger that, gents - thanks. Apparently, I haven't gotten it "hot", yet, so... ha ha.

 

[spife7980]

I shoot in groups daisy chained, I'll shoot one of each of my 5 charge weights starting left to right with a couple minutes in between each shot, long enough to check out a thread on here for updates or refresh my instagram for some new memes. Then when I finish those 5 I stop for 4 minutes or so, enough time to walk the 100 yards to look at the target and have a drink so I can take the can off and let it cool to avoid mirage that creeps up without mercy too much further past those 5 shots. I will then start at the end of the charge weights I stopped on and shoot right to left back across them. I figure doing so keeps everything pretty even without favoring one end of the weights and also mitigating the mirage and barrel heat. If I cant put the meat of my hand on the barrel without an impulse to remove it due to heat I wont shoot the next shot. Things heat up quickly here in the Texas sun even in January sometimes. A warm barrel is what we are going for, a hot barrel just leads to premature wear.

 

[davere]

Things heat up quickly here in the Texas sun even in January sometimes. A warm barrel is what we are going for, a hot barrel just leads to premature wear.

I used to take a tray for my cooler when I was practicing for USPSA matches in the summer when I lived in Austin. 100 rounds or so, and the gun would go on the tray in the cooler with the slide locked open while I reset targets and reloaded mags. Good times... ha ha.

 

[spife7980]

So Ive still been having issues with the 70 gr RDF so I figure why not try to use this chrono method.

70 RDF
Lapua 223
IMR 8208 XBR
CCI 400 [IMG2=JSON]{"data-align":"none","data-size":"full","height":"881","width":"661","src":"http:\/\/i.imgur.com\/LLYten9.jpg"}[/IMG2]
[IMG2=JSON]{"data-align":"none","data-size":"full","height":"494","width":"659","src":"http:\/\/i.imgur.com\/MmkI97E.jpg"}[/IMG2]



Shot with the magneto so its not so useful but the targets [IMG2=JSON]{"data-align":"none","data-size":"full","height":"501","width":"668","src":"http:\/\/i.imgur.com\/qj6FWch.jpg"}[/IMG2]



The meat and potatoes [IMG2=JSON]{"data-align":"none","data-size":"full","src":"http:\/\/i.imgur.com\/Xali8Kl.jpg"}[/IMG2]


So Im not really sure about what its telling me. Yall let me know if you have suggestions for the graphing.

At 22.6-22.8 red and green seem to level out but the blue doesnt and then at 23-23.2 the blue and green level out and the red doesnt. I was working 23-23.2 beforehand and could get some good groups but then I wold shoot them the next time to try and duplicate it and they would be horrible. Im sure annealing would help some but thats still waiting on annie to get it to me.

I figured I could upload the excel but no dice on that. Hopefully this copy paste of the cells will be easy to use if yall want to try some different stuff with graphing.

Grains	Series 1	Series 2	Series 3	Average	Max	Min	ES	SD
22	2574	2551	2561	2562	2574	2551	23	11.53256
22.2	2578	2564	2594	2578.667	2594	2564	30	15.01111
22.4	2598	2629	2608	2611.667	2629	2598	31	15.82193
22.6	2633	2649	2663	2648.333	2663	2633	30	15.01111
22.8	2661	2636	2666	2654.333	2666	2636	30	16.07275
23	2682	2702	2707	2697	2707	2682	25	13.22876
23.2	2692	2727	2712	2710.333	2727	2692	35	17.55942
23.4	2755	2716	2733	2734.667	2755	2716	39	19.55335

 

[Sheldon N]

Nice, the one thing I would offer in terms of data analysis is that you're really only interested in the "average" trendline for velocity since it removes some of the inherent variability from shot to shot. You can remove the other lines from the graph by right clicking them and selecting Change Series Chart Type and making it an ordinary scatter without a line. Then you'll have the data points but only the average line on the graph.

Would look like this.

Based of this there's a flat spot centered around 22.7g and 2650fps. The range of 23 -23.2 seems like the second most promising. However all the charges seem to have similar SD and none are great. Do you think there's any opportunity for improvement in powder measuring accuracy or neck tension consistency?

 

[spife7980]

Neck tension, certainly. Powder are just charge master drops. Annie should get here next week but my other brass has more firings and still shoots better. I am looking forward to seeing it's effects. I think I'll explore shooting a few tenths above and below the 22.7 just for thoroughness.

I like that with the lines removed. I couldn't figure out how people were doing it with the dots and single line combined but now I know it's just format trickery. I tried every excel chart option lol

 

[CharlieNC]

Chrono and targets don't agree.

 

[supercorndogs]

Chrono and targets don't agree.

The creator of the OCW test did warn against using chronos in this fashion to find nodes. I alway find my charge, tune my length, then chromo to confirm a low SD.


"Recent conversations with very learned mechanical
engineers are affording me some better understanding of
just why an OCW load works so well in the majority of
rifles chambered for the cartridge at hand.
Here are some of the major points coming to light:
Uniformity of velocity (meaning low extreme spreads of
velocity) are definitely not an indicator of the OCW
zone. We are actually finding that in many cases the
OCW zone does not have the tightest numbers--at least
initially. Fine tuning of the recipe with seating depth
variations and primer changes will improve the velocity
consistency, but simply shooting a succession of
graduated charges over the chronograph and looking for
a tight velocity spread will not lead you to the OCW."

 

[CharlieNC]

Spife I have not shot 8208, but in all the other powders I've assessed the good nodes were at much higher velocity.

 

[spife7980]

Well Im shooting this in a 16" so high velocities arent ever really going to be in play here and while my original 4064 load was right at 2750 without pressure signs I found that anything too much more than 23.5 of 8208 is giving me loose primer pockets prematurely. 23.7 had them loose-ish after one firing. No tight extraction or ejector smear but I can tell which I shot hard while priming them up again.

And going off of graphs may not work but its interesting me to put it to the test and hopefully give us all something tangible to look at. I had a couple 1/2 and 1/4 groups in that 23.1-23.2 area that I had identified as a possible spot but then the next round the following weekend they were back up to 1 moa or even larger sometimes. These RDFs are a bia that I havent been able to develop via traditional method and I dont mind wasting some shots to burn up my stock of 1200 of these. Im now at the point that I think the bullet and the barrel just dont agree with one another so I consider it already sunken costs, might as well use them up.

 

[CharlieNC]

I hear you Spife. When I first started shooting a number of years ago I was visiting master gun smith Dave Tooley and asking about how he developed loads for his new competition rifles. His advise was load a couple of "known" decent loads and if the bullet didn't shoot well move on to another bullet. Don't waste time and money on a bullet that does not show immediate promise.

 

[supercorndogs]

The following is ONLY my opinion based on researching these approaches over a couple of months. I claim no expertise.

It may be a subtle point, but I think the strategy to the chrono method would be to to look for the most stable average velocity across a contiguous range of charges rather than look for a charge (or range of charges) with the smallest SD/ES. As stated, SD/ES for the target charge could then be improved by various secondary means.

I suspect the range of charges with a stable average velocity would also show a stable point of impact in an OCW test. The difference being eliminating the human error from the test data.

Somehow I got the impression that the OCW method emerged from the hunting community. (I could be wrong on that.) Perhaps at the ranges they are operating in, barrel harmonic effects outweigh velocity variation? That would would explain the de-emphasis on velocity variation. Angular variation would have a linear effect over range, where-as velocity variation, since it effects drag, would have a non-linear effect over range. I suspect over long or extreme long range, velocity variation would begin to dominate in ways not seen at medium range.

Thats a funny long winded way of saying the higher your ES the bigger your veridical spread.

It seems like everyone always does one or the other. It would be interesting to run a full test of each with the same components and rifle back to back and compare the results.

OCW is not some half assed conception that came out of a need to hit a pie plate at 100y. It is possible that you are correct in looking for a flat spot across several charges is not what he is waring about.

http://optimalchargeweight.embarqspace.com

 

[lash]

Did anyone in this thread say that?

Thanks for the link, but I suspect most of us in this thread have already read his treatise. I believe what he was saying was that you simply can't fire a series of rounds at a range of charge weights and select the charge weight that had the smallest SD/ES. That doesn't necessarily represent an OCW. I agree. The OCW should have stable behavior relative to it's charge weight neighbors. That might be indicated by a series of charges with a similar POI, as in the conventional OCW method. I suspect that might alternatively be identified by a range of charged with similar average velocities. The similar average velocities might translate to a similar POI if it and been a conventional OCW test. The difference being, less chance of introducing noise to the data through human error.

I'm not implying the conventional OCW method is a poor approach. I'm simply suggesting the Chrono method might be a possible alternative to reach the same conclusion.

The difference between you and Dan Newberry is that he has actually worked with engineers and others to prove out his "treatise" and it has been successfully used by many, who actually bothered to take the time to understand it, since then.

You, on the other hand by your own admission have spent some time on the internet reading a bunch of stuff and are presenting your own theory based upon your great experience there. And this gives you the background to provide your alternative argument and suggest that his method might be flawed because bullets and barrels act differently for hunters than for real precision shooters like yourself.

I would love to see some of the extensive testing and data that you've done to back up your contentions.

 

[CharlieNC]

To move beyond being a theory, proof is required. I know Dan pretty well, and he worked somewhat with Chris Long who developed the Optimum Barrel Time concept to address the associated harmonics which is the driving force behind WHY something like OBT and ladder testing work. Many do not accept the OBT concept as the proper explanation, and focus more on the barrel "whip" type of harmonics. After many evaluations I have proven to myself that the OBT method works to get you very close, if not dead on, in identifying where the nodes are. While the longitudinal pressure wave concept may not be 100% accurate, the results are excellent. Same thing with tuners, the documented evidence is proof that barrel harmonics can be harnessed in this manner as well. Chrono only load development, I don't know. During load development I always measure chrono and cannot say it yields good identification of nodes vs the target for me.