Calling all OCW experts

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That sounds like a good idea ArchAngelCD. Would it be acceptable to delete to highest and lowest charges as well since they don't seem to be OCWs by most any measurement.
I spent about two hours running the test on Sunday so adding another ten rounds allowing a couple minutes between shots should keep me within my time limit. The range was busy with a lot of cease fires on Sunday which also added quite a bit of down time.
 
How do you separate human variables holding/shooting the rifle contributing to velocity spread from fast to slow and shot hole spread in all directions on target that is caused by the ammo and rifle alone?
 
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I always liked to shoot five shot groups because that is how I came up doing it. You must include all groups and all shots though. I was used to to concentrating for five shots, taking a break, shoot five more etc, but I have in the last three or four years shot some reduced target F Class where we shot 20 rounds each target. Either way, you get a big sample. A 20 shot group, or a 20 or 25 shot "aggregate". Either way it counts all shots. And of course it includes shooter error, both physical error and wind/mirage reading error. (Some days I just suck and pack up and go home.)

Ladder schmatter, OCW or whatever, we have to put shots on target and see what it does. That's all I have ever done to find a good load. Try things and shoot them a lot. Early on in testing (Not many shots) you may be encouraged, and it may hold up (Although it doesn't always), but you have to keep shooting and see.

And I have said for years here a good pistol load will shoot over a small spread. If 4.0 shots great but 3.9 or 4.1 doesn't, 4.0 was probably a fluke. It's no different for rifle, no great loads only shoot at "X" powder weight but not .1 up or down.

And with those great loads we will shoot the occasional screamer group, but then miss a condition and shoot a big one, or the law of averages catches up with us and despite our best effort we shoot a mediocre one.

But we see it all the time here where someone shoots one group with each charge weight and then asks which one is best. One group is meaningless. It may be worth pursuing, but it means nothing by its self.
 
THR has never led me astray so I think I may follow what seems like a general consensus here and reshoot the test with 15-20 rounds of each load. I'll probably drop the lowest and highest loads and load 20 of each of the other five. I'll shoot 15 rounds of each and save the last five rounds for further testing. I'd give anything for a range that was closer.
 
Regarding the shooter's variables.....

There was a target rifle shooting organization comprising several countries who had all competitors be issued the same make/model military rifle and same lot of arsenal ball ammo for a given match. Rifles were shot from prone at 300 to 1000 yards. That was the governing body's reasoning to level the playing field and determine who was the best marksman. Rarely did someone get the same rifle for each local match and it was luck of the draw for international matches for all countries. Interested people in the armory issuing ammo and rifles sometimes tracked each rifle by serial number versus scores shot with it. Naturally, some rifles were very accurate and others were not. Do you think they ever issued the most accurate rifles to the home teams?

The rules were changed decades later to let people use their own rifles but still issued the same lot of arsenal ball ammo to everyone. Hand loads were considered an unfair advantage.
 
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I've been reading and rereading these posts and studying the Audette (ladder) and OCW methods so much that I think my head is going to explode. My conclusion which fits my situation and is only my opinion, is that a combination of both methods will yield the best results.

I've already shot the OCW test and plotted results but I hadn't plotted them linearly like Varminterror does. When I did, it indicated a leveling of the wave between the consecutive charges of 41.8, 42.1 & 42.4. This is the node that I'm going to take and use the ladder method on. Because of time constraints at the range I'm going to load fifteen of each of the three charges and shoot twelve of each at three targets and evaluate these based on each twelve shot group, arriving at my final load which I'll then tune for seating depth. I'll reserve three of each load for a "shoot off" if necessary.

I know this may not be the best solution but I see merit in both methods. I like the fact that the OCW method doesn't look at individual shots but in group centers which evens out some of the variables even though it's only three shot groups. I like the ladder method because once I have my final load narrowed down to a range of 0.6gr, I can make a final determination based on individual shot performance and no matter which way I end up I can't be too far off which is one of the basic premises of the OCW.

A better final test would be to run it at 300 yards as it's designed for but I'll make do with what I have. I'm pretty confident this will work for me. I'm also confident there will be room for further tightening by varying seating depth since the ogive to base cartridge length I'm working with now is 0.70 off the lands in my rifle.

Thanks to everyone for your input which has really been helpful. I'll check back in after the test (hopefully only two weeks from now) and let you know how it went.
 
We've argued this over and over again in many threads. Personally, I think that the vertical POI dispersion that occurs as you increase powder weight on a load is more likely due to minute changes in the angle of the muzzle caused by mechanical deflection over the course of the firing process. Varmint Als website has an interesting FEA showing this delection. So while I personally think that the OCW theory of a bore enlarging shockwave traveling up and down the barrel causing group changes is false, the OCW can still be beneficial for leading you to a barrel timeframe where the muzzle deflection rate is relatively low. In my experience, the OCW helps you narrow down your focus to a window of powder weights that is LIKELY to be forgiving. Like anything else probabilistic, it's not 100% you're trading some certainty (accepting a lower confidence) for economy. There is still a good amount of verification that needs to be done even if you've found what looks like a promising charge weight.

It's fine to only use loads worked up and proven by someone else if you're satisfied only shooting the cartridges, bullets and powders most commonly used by "they". If you want to use other cartridges or even just other components, you have to employ some method to test them. If you're not willing to accept any confidence level less than say 95% when doing initial screenings, then you'll have to shoot 20 of every powder weight your interested in. If you can accept a lower confidence level during initial testing, you can decrease your group sizes some. Is 90% confidence enough? 85%? It's been a while since my prob/stat classes, but it seems like most statistical discussions here on group size skip right over the topic of confidence intervals.

I'd shoot some more in the 42.1gr range and see what happened.
 
tcoz said:
. I'm also confident there will be room for further tightening by varying seating depth since the ogive to base cartridge length I'm working with now is 0.70 off the lands in my rifle.
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I don't think there's any significant difference in accuracy with shoulder fired rifles with ammo loaded to some OAL as the throat erodes away down the barrel several hundredths inch as the barrel wears out. Top level competitive shooters with bullets seated to a fixed round OAL for loading from magazines see no significant loss of accuracy for the 3000 round life of a 308 Win barrel.

Are you going to seat bullets .001" shallower in the case every 30 shots to keep biller jump distance spread that much?

When testing ammo for accuracy at ranges less than 500 yards, I think it's a waste of components to increment charge weights less than 2%.
 
Gtscotty said:
..So while I personally think that the OCW theory of a bore enlarging shockwave traveling up and down the barrel causing group changes is false, the OCW can still be beneficial for leading you to a barrel timeframe where the muzzle deflection rate is relatively low. In my experience, the OCW helps you narrow down your focus to a window of powder weights that is LIKELY to be forgiving.
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And this is exactly what I feel that I got by shooting the OCW test...a window to narrow further testing.

I'd shoot some more in the 42.1gr range and see what happened.
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Exactly. As I mentioned in my previous post, my further testing will be at 41.8, 42.1 and 42.4.
 
Bart B. said:
I don't think there's any significant difference in accuracy with shoulder fired rifles with ammo loaded to some OAL as the throat erodes away down the barrel several hundredths inch as the barrel wears out. Top level competitive shooters with bullets seated to a fixed round OAL for loading from magazines see no significant loss of accuracy for the 3000 round life of a 308 Win barrel.
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That's what I'm interested to find out. I've never played around with seating depth before. I'm somewhat skeptical because match ammo is seated to a depth that shoots accurately in a wide variety of rifles and the Hornady Match that I took my initial seating depth from is a .075 jump in my rifle (Savage 10 FCP-SR) which by most accounts won't allow for exceptional accuracy.
 
Do you want your test groups to have at least a 90% level of confidence of representing the loads accuracy all the time?
 
Bart B. said:
When testing ammo for accuracy at ranges less than 500 yards, I think it's a waste of components to increment charge weights less than 2%.
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Interesting you should say this. I tend to agree. A friend and I were talking while at the range last week. He used to reload years ago but has not loaded a cartridge in 20 years, and I'm relatively new ( 4 years) to it. As I shot a couple really nice groups for me out of my AR he asked what the loads were. That lead to the question of when I test what do I increment my loads by, and I said generally rifle .5 gr and pistol .2. I told him it "depends" sometimes, but my theory was that with a hunting rifle shooting at 100 yards I wasn't good enough or the rifle wasn't good enough to be able to see any differences at increments less than .5 grains. He largely disagreed with me and said I could be missing a node. I just told him you can waste a lot of powder and components chasing something that isn't there. Your 2% number is close to what I've been doing for my rifle loads. I can generally find a decent load for me with that rule of thumb.

-Jeff
 
Bart B. said:
Do you want your test groups to have at least a 90% level of confidence of representing the loads accuracy all the time?
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80-90% confidence is probably the best I can hope for using my procedures. I feel that I can largely take charge weight variation out of the equation. I use a Chargemaster and I'm pretty anal about charge accuracy. I verify charge weights against a beam scale about every 15 or 20 charges and it's usually spot on. Also, if the Chargemaster overthrows even 0.1gr I toss it back into the hopper.
Temperature and other factors are where my confidence isn't as high.
 
Bartojc said:
I just told him you can waste a lot of powder and components chasing something that isn't there.

-Jeff
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Too true. I've found that some bullets, the 125gr SMK in particular, shoot incredibly well over a wide charge band. Up to 3 whole grains in one case. Sometimes we make things far more complicated than they need to be.
 
It's been several years since I've tried to make hunting rifles shoot through the same hole however it can be done. The nodes that done it usually wasn't large. & It will disappear after a while. Maybe 300 or as much as 500 shots. The rifles I've done this with doesn't have deep throats & with a new rifle I start about 10ish off the lands if the magazine permits.

I don't chase the lands. That's just where I load. I've had better luck with this ballpark measurement then fallowing a manual.

Does the shoot groups open up because I'm not chasing the lands? I think it's likely. Is there another reason involve? I think that's even more likely.

I used to hate automatics because I thought 1" groups were unacceptable. However in later years I've come to enjoy them.

I haven't really found trigger time as a waste. I do keep finding my goals & interest changing tho.
 
25 shots per test is needed to have over 90% confidence representing the group size all shots will shoot inside of.
 
Bart B. said:
25 shots per test is needed to have over 90% confidence representing the group size all shots will shoot inside of.
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Can you post the math you used to derive this number? I'd like to read the analysis. How many shots are needed to establish that any given shot from the same sample has a 90% probability of landing inside a given interval? I think this is a slightly different question. What interval was used for your calculation? Is saying that a certain number of shots are required to establish that one load is without a doubt better than another at a certain confidence level the same as saying that there is no likelihood that useful direction that can be gained from any group of smaller size?
 
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kingmt said:
I used to hate automatics because I thought 1" groups were unacceptable. However in later years I've come to enjoy them.

I haven't really found trigger time as a waste. I do keep finding my goals & interest changing tho
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My best groups ever have come from my one semi-auto (discounting .22 LR) which is surprising to be. I get good enough groups from my bolt actions for me, but they are largely stock hunting rifles with stock triggers. More trigger time has made my groups better. I truly believe it's not all reloading related, but more to do with the time shooting and better technique. Either way it's fun, and I never tire of trying to get better.

-Jeff
 
Bartojc said:
My best groups ever have come from my one semi-auto (discounting .22 LR) which is surprising to be. I get good enough groups from my bolt actions for me, but they are largely stock hunting rifles with stock triggers. More trigger time has made my groups better. I truly believe it's not all reloading related, but more to do with the time shooting and better technique. Either way it's fun, and I never tire of trying to get better.

-Jeff
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What is"good enough groups" this changes for me depending on what I'm doing.

Everyone's standards for good enough seem different.

As far as hunting rifles go that is all I've ever used. Some are easy to find loads for while others are picky. I've never had a bolt rifle I couldn't get under 3/4"groups at 100 yards tho which is good enough for me.
 
The standard ladder test tells you nothing about the accuracy of a particular load. It only tells you where the shots hit in relation to other loads.
OCW is just one guy cobbling information from the Internet to create a lot of nonsense and is unsafe. Assumes the assorted ballistics engineers don't know what they're doing and a WHAG is good enough too.
For example, if one does the following(from the OCW how-to) and chooses the Lee and Hodgdon manuals, you're looking at Hodgdon's data only. Lee tests absolutely nothing themselves. Everything they put in their branded manual comes from the powder makers in most cases.
"3. Consult at least three load data sources for maximum charge weight for the powder you've selected. Powder manufacturers are the most reliable source. You must then decide on what your maximum charge will be."
The guy's load data page shows data for a 70 grain .243 that's over max too. Hope he's got lots of liability insurance.
"Use magnum primers only with magnum chamberings..." Magnum primers have nothing whatever to do with the cartridge name. They're about the powder used only.
"...alter the burn rate of the powder..." Utter nonsense. You cannot alter the burn rate of any powder by warming it.
"...establish an "accuracy standard"...Spend 20 dollars on a box..." If you're not reloading, finding the most accurate factory ammo in your rifle requires trying a box of as many brands and bullet weights as possible. Your rifle may just dislike the brand you picked.
"...When in doubt, consult the Nosler manual..." Lyman's manual has an 'accuracy load' too.
 
Sunray said:
The standard ladder test tells you nothing about the accuracy of a particular load. It only tells you where the shots hit in relation to other loads.
OCW is just one guy cobbling information from the Internet to create a lot of nonsense and is unsafe. Assumes the assorted ballistics engineers don't know what they're doing and a WHAG is good enough too.
For example, if one does the following(from the OCW how-to) and chooses the Lee and Hodgdon manuals, you're looking at Hodgdon's data only. Lee tests absolutely nothing themselves. Everything they put in their branded manual comes from the powder makers in most cases.
"3. Consult at least three load data sources for maximum charge weight for the powder you've selected. Powder manufacturers are the most reliable source. You must then decide on what your maximum charge will be."
The guy's load data page shows data for a 70 grain .243 that's over max too. Hope he's got lots of liability insurance.
"Use magnum primers only with magnum chamberings..." Magnum primers have nothing whatever to do with the cartridge name. They're about the powder used only.
"...alter the burn rate of the powder..." Utter nonsense. You cannot alter the burn rate of any powder by warming it.
"...establish an "accuracy standard"...Spend 20 dollars on a box..." If you're not reloading, finding the most accurate factory ammo in your rifle requires trying a box of as many brands and bullet weights as possible. Your rifle may just dislike the brand you picked.
"...When in doubt, consult the Nosler manual..." Lyman's manual has an 'accuracy load' too.
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Did you really think before posting this?

For reloaders that wasn't too stick to printed data & just mock it then I say to them have fun. But why would I ever look at data from three different people & then just guess at which one I should trust more.

I have my doubts that any of the major powder or bullet manufactures would ever post anything above SAMMI specs. However max in a manual only means where they stopped for whatever reason they decide to stop there. Often it has nothing to do with max SAMMI pressure.

Advice on going to buy factory ammo would only help if your going to copy bullet, powder, primer, & brass the exact same as they offer which isn't likely.

If your statement is how you do things then great but your ideas aren't real life. Everyone should learn to read signs of pressure on a case. Most of the times I've shot factory round I see more pressure then I'd be willing to use. I like to make my brass & gun last as long as I can.
 
Just my .02 cents worth. I think you are much better off to shoot at 200 yards.

100 yards will just not give you the very visible patterns you will pick up easily at 200 yards.
 
Coltdriver, as the OP, I'm assuming your comment is directed to me.
I'd love to shoot at 200 or 300 yards but the only range I have access to is 100 yards.
 
Bart B. said:
25 shots per test is needed to have over 90% confidence representing the group size all shots will shoot inside of.
Click to expand...

Gtscotty said:
Can you post the math you used to derive this number? I'd like to read the analysis.
Click to expand...

I'm not trying to be snarky but any good statistics text book will provide the answer and math. I'm afraid I remember enough about statistics to be dangerous these days and before retiring, I let the statisticians at my work do the math.:)

There is not a simple answer but the greater the points in the data set, the more confidence in its results. But the greater number of points, the greater the cost to accumulate the results (time, material, man hours, etc.).
 
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