OCW method , my first honest try . Come take a look and help .

[rondog]

OK, what does "OCW" mean?

 

[LiveLife]

To me, Optimal Charge Weight essentially means working up loads higher than start charge (7% - 10% from max) in .7% - 1% increment (.2-.4 gr) and using 3 shot groups at 100 yards to identify a pattern of smaller shot group node to further tweak the charges (3 loads at .1 gr increment) at 200+ yards and other variables (COAL, neck turning etc.). I am not familiar with OCW so someone more knowledgeable can better explain.

Optimal Charge Weight nodes explained in this video along with another variable of Optimal Barrel Time nodes discussed and using QuickLoad load table to match the OCW and OBT nodes for determining accuracy nodes.

However, error in load table is mentioned due to factors like chamber/reduced internal case volume of thicker walled military case/water weight capacity/type of brass etc. and chono data was used to match up muzzle velocities with powder charges that produced accuracy nodes.

Video ends by saying there's no right or wrong on this ... a lot of trying to see patterns ...

[YOUTUBE]8hzcxytpKWU[/YOUTUBE]

Video response showing more clear accuracy node from OCW

[YOUTUBE]8fW9zNKeqSI[/YOUTUBE]

 

[readyeddy]

All of those groups look good to me. Are all of you guys shooting sub moa?

 

[LiveLife]

OP's target posted with 6 shot groups is from 200 yards. OP started testing with 39.0 gr, 39.8 gr, 40.6 gr - Perhaps they were shot at 100 yards and produced sub-MOA groups and OP could clarify for us.

I don't start fine tuning a load for 500/600 yards until initial test result in sub-MOA results when I was doing the OCW tests.

In the fine tuning, you should get 3/4-1/2 MOA results at 400 yards.

 

[LiveLife]

So what does these targets say to you and where is my OCW ??

[Lake City Long Range brass: 41.4, 41.8, 42.2, 42.6, 43.0, 43.4 gr IMR 4895]

You probably skipped over a best load....

Since the initial back off of 10% from max did not factor in use of smaller internal volume LC LR case, there was error in charge weight calculation (as Lyman #49 recommends reducing max charge by 1 to 2 grains when using thicker walled military cases).

So if max charge was reduced by 2 gr from Hodgdon's 44.0 gr compressed charge (meant for larger case volume Winchester brass) we get 42 gr as new max charge and using 7% reduction we get these OCW charges:

1 - 39.2
2 - 39.6
3 - 40.0
4 - 40.4
5 - 40.8
6 - 41.1
7 - 41.4
8 - 41.6
9 - 41.8
10 - 42.0

And if max charge was reduced by 1 gr for corrected 43 gr and used 7% reduction we get these OCW charges:

1 - 40.1
2 - 40.5
3 - 40.9
4 - 41.3
5 - 41.7
6 - 42.1
7 - 42.4
8 - 42.6
9 - 42.8
10 - 43.0

I am not too familiar with OCW so someone more knowledgeable correct my calculations.

 

[Metal God]

Are all of you guys shooting sub moa?

Yes or at least that's what we are striving for . If I can't get a load combo to shoot consistently sub moa . I'll change a component or abandon it all together . Now that's target loads . I have a couple hunting loads that are a tad over 1moa but those I pushed to max velocity while still keeping good accuracy .

And if max charge was reduced by 1 gr for corrected 43 gr and used 7% reduction

I used 43.3gr as my max charge and reduced be 10% . Can you explian again why if I did not hit max pressure and all my loads were safe . It's still important to reduce the load ?

That's kinda what I have been trying to say in my previous posts

lol I know exactly what you've been saying . I felt you did not realize what my points were . As for testing with RL-15 instead of 4895 . Couple things there , I don't use RL-15 much and don't have enough to run the test to it's conclusion . I use 4895 as my plinking powder because I have lots of it . IMR 4064 is my go to accuracy powder . I have every intention of running a traditional load development with the same components at the conclusion of the OCW test to see if I find the same charge .

 

[joem1945]

I find my most accurate loads for a given caliber and bellet weight will be between 92% and 98% of the max load data. Sometimes there will be 2 or 3 nodes in that range but mostly 2.

 

[LiveLife]

I used 43.3 gr as my max charge and reduced be 10%. Can you explian again why if I did not hit max pressure and all my loads were safe. It's still important to reduce the load?

If 43.3 gr was used as max charge, then 10% reduction should be 38.9 gr? (I used 7% reduction to come closer to your charges)

The sample 10 OCW charges I posted were from online calculator spreadsheet where 39/42 gr and 40/43 gr charges were used and incrementally decreased charge difference from .4 gr to .2 gr as approaching max charge. And this spreadsheet did not go over max charge.

As jwrowland77 posted, I think lower charges should have been used to identify all the accuracy nodes.

And since I am not familiar with OCW, someone else could certainly explain better and I could be wrong.

 

[Metal God]

I'm sorry I should have been more clear . I was speaking to reducing the charge because of case volume concerns . I feel I've explained why the test was done at the upper range . The first video you posted explained the same thing . For long range shooting ( which I believe this method was developed for ) Finding a node at a velocity that is unable to achieve your objective is not all that helpful .

I said right off the bat I'm a skeptic of this method but would give it an honest try . I feel being true to the test would be not to change any part of the test . I'm not looking for someone to challenge me on the method , You'll just be preaching to the choir . I'm looking for someone to explain why my/our concerns are not valid when using the OCW test .

I how ever need to finish the testing process and see if it works . I've had a few guys now say the 42.2 to 42.6 range is my OCW . I'll continue there and see what kind of results I get . I may very well finish these test and conclude it's the best thing since sliced bread .

 

[LiveLife]

You maybe right.

Was there an initial testing at 100 yards and how big were the shot groups?

If OCW test was not done at 100 yards, perhaps another OCW testing at 100 yards may provide better data?

 

[Metal God]

Was there an initial testing at 100 yards and how big were the shot groups?

touche , haha see there, I did change something I only shot at 200yds

I guess I'll start over but will still try the 42.2 to 42.6 loads and see what I get .

 

[macgrumpy]

I thought that the concept of the OCW method was to find a load that produced CONSISTENT group sizes regardless of slight variations in cartridge components, not necessarily the smallest groups. Dan's original claim was that he wanted a load that he could trust from one powder/bullet/case/primer lot to another, in other words, he wanted to know that he had a load that would perform the same way over the years so he didn't have to develop a new load every time he changed component lots.

At any rate, I became frustrated with the OCW identification process too, I had a hard time telling what groups were doing what. I later realized that my problem was that I was using a battle rifle and it just wasn't accurate enough, it's inherent inaccuracy clouded the issue so bad that I had a hard time seeing the patterns in my groups. But I did find a pearl in the mud, Dan talked about accuracy nodes and I thought I might be able to use my QuickLoad software to find that node based on barrel time rather than impacts on paper.

Once I get the best load (regardless of how I got there, OCW, ladder test, it doesn't matter) I run the numbers through QuickLoad being very careful to put in valid data (actual case volume, corrected muzzle velocity, atmospherics, etc.) and then I record the barrel time. The barrel time becomes my guide to good loads for that rifle (yes, it changes with every rifle due to harmonics and other physical factors). Unfortunately it doesn't help with finding that magic load that Newberry wanted, I have to adjust my loads for every lot change, but at least I can tune a load pretty quickly and I can get some very nice results in a an old battle rifle. Someday I'll get a nice bolt action rifle and I'll have to start experimenting all over again.

I know it doesn't help you with what you are trying to do but I thought it might help to know that others have had the same frustration with the OCW method. I like Dan's idea but it doesn't work for all types of rifles or all shooters either.

 

[jwrowland77]

OCW test still work at 200yd. Actually you'll get more accurate results by giving time to let bullet settle in.

Give an honest try by using smaller increments in your powder charges.

 

[Metal God]

I thought that the concept of the OCW method was to find a load that produced CONSISTENT group sizes regardless of slight variations in cartridge components, not necessarily the smallest groups. Dan's original claim was that he wanted a load that he could trust from one powder/bullet/case/primer lot to another, in other words, he wanted to know that he had a load that would perform the same way over the years so he didn't have to develop a new load every time he changed component lots.

That's been my understanding as well . I remember back when he was on all these boards talking about his chocolate cake and explaining how and why it works . He would explain how his method would/should give a rather wide charge zone where environmental or small component changes would not effect consistency . I now see guys talking about working loads up in .1gr or .2gr increments . If .1gr or .2gr is going to throw your load out of wak then you are not in that zone the OCW method is supposed to find IMHO

Once I get the best load (regardless of how I got there, OCW, ladder test, it doesn't matter) I run the numbers through QuickLoad being very careful to put in valid data (actual case volume, corrected muzzle velocity, atmospherics, etc.) and then I record the barrel time. The barrel time becomes my guide to good loads for that rifle (yes, it changes with every rifle due to harmonics and other physical factors).

It's funny you bring this up . I believe bds was touching on this as well . After over 3k rounds through this rifle I used in the test . Many many of those rounds over a chrono with multiple different components . I have found a velocity zone that works better then anything else . Not that I work up a load to a specific velocity but over time and many different loads I have found that my best loads regardless of components ( to a point ) group best with a muzzle velocity of 2550fps to 2575fps . That clearly goes to barrel harmonics and barrel whip .

I've not done extensive research into my notes but that velocity node seems to swing around every 200fps . I've had nice loads around the 2350fps zone as well as the 2750fps zone . I keep pretty detailed notes on every load I've developed along with the targets . They all get stored together in a binder . There has been quite a few things or patterns I've noticed over the years by going back and just looking at the data as a whole . The velocity thing above was one . Another that stands out is that I was shooting double groups in the same sting of shots.

4 shots


4 shots


10 shots


Those were shot over a year or longer . I'd see those come up but not all the time . One day I was looking through all my data and noticed the pattern well after I'd moved on . All those groups were shot using the same rifle . At the time I was having A REAL hard time finding consistent loads for that specific rifle .

I'd work some loads up think I'd find a good load . How ever when I went back to the range to confirm the good loads they would often shoot very bad . This is why I went back and started looking at ALL the previous data to see what may be going on and that's when I noticed the double group patterns .

Anybody want to take a stab at what the problem was ????

 

[Dave P]

MG - now you are cooking.

Those earlier pictures looked like larger groups than you measured. Sorry.

 

[Metal God]

see there, I did change something

I changed something else . I did not realize I did until today . I shot one shot per charge and let the barrel completely cool in between each shot . This made every shot a cold bore shot . I did not know round robin meant shoot one shot from each charge in a row letting the barrel heat up . I was under the impression that each shot had to be in the same conditions as the last shot .

 

[Metal God]

No takers on the double groupings ???

It was my action screws were loose and or would come loose . It was one of those things I never really thought about . I knew torque settings can effect rifle performance but never thought the screws were coming loose . Used a little blue loc-tite after a torque test and the double groups have never returned

 

[macgrumpy]

I work with M1A rifles more than anything else and I've spent years working on how to make them accurate. One of the symptoms I ran across was the same kind of pattern, two distinct groups. Through research I've found several sources that explain that when we troubleshoot groups we have to remember that two separate groups is usually an indication that there is a mechanical issue with the rifle - something is loose.

The best explanation that I've come across says that you have remember that the stock is an extension of your eye line while the bore is an extension of the bullet's line of departure. Since these are two separate parts they must stay in the same relationship to each another for each shot to go in to the same trajectory. Loose action screws allows the center axes of these two parts to change their relationship to each other. After each shot the two axes "pop" back and forth out-of and in-to alignment. Because they can only move as far as the loose fit of the screws will allow you get impacts that move the same amount from shot to shot. They are bouncing back and forth.

And by the way, those two groups have always been on a horizontal or diagonal line for me, I've never seen one in a vertical line but I suppose it can happen. Probably a loose sight would cause more of a vertical line between separate groups.

 

[LiveLife]

explain why .2 gr is going to swing this test

The way I see it, OCW uses .4-.2 gr charge differences to get you in the ballpark of accuracy nodes. Once these nodes are identified, .1 gr charges are used to narrow down the smallest group at greater distances. Then OAL/seating depth is used to further decrease the group size.

I don't start fine tuning a load for 500/600 yards until initial test result in sub-MOA results when I was doing the OCW tests.

You'll get a accuracy node where you'll have three round (even with different charges, lined up horizontally.

Once you get that, pick the middle load and then fine tune your OAL. It's that simple.

In the fine tuning, you should get 3/4-1/2 MOA results at 400 yards.

And the key is changing only one variable at a time. You posted identifying several variables. When fine tuning the load with .1 gr charges, other variables must remain fixed or will effect group size.

Ultimately, it's the holes on target that matters. If the groups continue to shrink and remain small, then you must be doing the right thing. If the groups don't shrink, then your process/method is in question.

So OCW in a nutshell - if .4 to .2 gr charge difference groups at 100 yards (or 200) show pattern for accuracy nodes, fine tune the nodes with .1 gr charges to obtain smallest group size then adjust OAL to further decrease the group size.

Is that about right?

 

[Paladin7]

Not sure if someone said this already, but OCW tests should be done at 100 yards.

I would suggest doing the test again, this time at 100 yards. This will eliminate any issues with wind deflection, etc. and give you better results.

 

[grubbylabs]

To be honest, I am sold on the ladder test. If you can get a 300 yard range, it's the way to go. It takes about 20 rounds to get figured out.

You can read up on it via the Google function on your PC. And I have even seen a good YouTube video.

8541 tactical on you tube does a good video on it.

This is 3 3 shot groups I shot after finding my load using the ladder test.

The 3rd group, the worst was because I was playing with the magnification of my scope. I went from 8x to 16x.

Regardless of your method, you have to be willing to accept that a given bullet, powder, primer, and brass combo just might not work for your rifle.

 

[Andrew Leigh]

Deleted.

 

[Paladin7]

The Ladder Test is a good one, but it doesn't factor in differences in pressure that will affect how a load performs in the field vs at the range, hence the OCW (Optimal Charge Weight) test.

OCW is used to find a load that is more pressure resistant, so POI doesn't change as much when you are shooting in warmer temperatures at the range, then use the same load in the field in much colder temperatures.

The trick to OCW is to find the node in the middle of groups that are consistent in POI. Therefore, if pressure increases or decreases, most likely due to temperature changes, the POI will remain relatively the same at distance.

The OCW test needs to be conducted at 100 yards, to minimize variables such as wind drift, which is more of a factor past 100 yards.

Hope that helps...

 

[Metal God]

After you have fired the sighters and confirmed that there are no pressure signs (hard bolt lift, flattened primers, etc.) you allow the barrel to cool for an adequate amount of time (use common sense--the hotter it is outside, the longer it will need to cool) you will then fire your first shot from the first group of the graduated charges. You fire this shot at target number 1.


Allow the barrel to cool, then fire a shot from the second graduation at target number 2. Wait for cooling of the barrel, then fire a shot from the third graduation at target number 3. Continue this "round robin" sequence until you have been through all of the targets three times. At this point you will have a three shot group on each of the targets.

Just re-read the directions and letting the barrel cool after every shot is the correct way to run this test . Turns out at least I did that right .

The other thing I've noticed after reading now many articles and or post on this subject . The increments in which you go up are proportionate to the size of the cartridge . It's very common to see .3gr for 6BR / .4gr for 308 / .5gr for 30-06 all the way to as much as 2.5gr increments when testing the 50 BMG . Not only that but the directions say move up in .7% to 1% increments . 1% of 40gr is .4gr so again I was right where the directions say you should be .

This leads me to believe the only thing I really did wrong was shoot at 200 yards . The more I think about it . The fact this test does not really evaluate group size but vertical stringing . Me shooting at 200 yards is not that big of a deal breaker . There was some wind that day but not much do to the angle . Even at 90* the wind would only effect the horizontal POI and not the vertical POI so the results should be usable .

Assuming you all buy into that we now go back to reading the targets .

I've noticed something interesting .



If you look at the target , it appears 42.2 to 42.6 are the most consistent . But are they really ? When you look at the actual distance they are from POA to POI in relation to the "center" of the 3 shot group .

I have the measurements of the centers of the triangles
41.4 is a straight line so I'm not sure where the center is ?
41.8 - 2.340 high x .040 left
42.2 - 2.040 high x .610 right
42.6 - 3.040 high x .520 right
43.0 - 2.825 high x .255 right
43.4 - 3.045 high x .725 right

42.2gr is a full inch lower then 42.6 now is the bullets hitting higher do to the +.4gr of charge or is it that they are not really the zone I'm looking for ? Sure each group separately appears to have less vertical stringing but compare them to each other and there is a full inch difference .

Now look at 42.6 through 43.4 . Now the individual groups don't look as good as the lower charges in relation to there individual vertical string . Now compare there centers and you get a whole different picture . If you calculate and compare the centers of 42.6 through 43.4 there is only a .22" difference between all three .

So which should I believe ?

14. Triangulate the groups. This means to connect all three shots in a triangular form, and determine the center of the group, and plot that point on the target. Measure this point's distance and direction from the bullseye, and record the information somewhere on the target. Do this for all of the targets. If you have a called flyer, you should discount that shot, or replace it in the group if you have an additional round loaded with that charge.

15. You will now look for the three groups which come the closest to hitting the same POI (point of impact) on the targets. The trend of the groups should be obvious, normally going from low and favoring one side, to high and favoring the other side. But along the progression, there should be a string of at least three groups that all hit the target in the same relative point.

16. After you have carefully measured group sizes and distances and directions from the bullseye, you will know which three groups come the closest to hitting the target in the same POI. You now choose the powder charge which represents the center of this string. For example, if 34.7, 35.0, and 35.3 grains all grouped about 1.5 inches high, and about 3/4 of an inch right of the bullseye, you would choose the 35.0 grain charge as your OCW (optimal charge weight). This charge will allow 34.7 and 35.3 grain charges to group right with it. This will be a very "pressure tolerant" or "resilient" load.

 

[Paladin7]

If we put the 200 yard testing aside, Looking at your targets, I would focus on a 42.8 grain load, set my sights accordingly, and begin working on bullet seating depth to dial in that load and make it as accurate as possible.

As a general rule, for hunting purposes, I would want the higher end loadings to get the most velocity I could get.

Bullet seating depth should tighten that group nicely.

Let us know how your further testing works out.