Help Interpreting OCW Results

[bluebie]

Hey Guys, I just did an OCW test on 10 handloads with a 0.3gr increment increase in charge weight. Which load would you select out of the ones here? The picture is sidways, so groups are numbered like this:

3   1
  5
4   2

8   6
 10
9   7

They all seem to have a pretty similar POI, which is kind of frustrating haha. I will also add that I was getting a bit of sticky bolt lift on charge #10, which is at 42.7gr H4350 (6.5 creedmoor). So, I am hesitant to actually use that.

Let me know if the pic is too cluttered, or if viewing sideways is a pain in the ass. I can upload another one.

I'm going to guess and say that good segment is [4, 5, 6] what do you think?

 

[spife7980]

Youre right, that is really busy and hard to tell with so much yellow splashed everywhere.

 

[Fig]

The smallest group with the lowest SD/ES? Just a guess...

They're all sub 1/2 MOA. Looks like it doesn't matter what the load is the rifle shoots lights out.

 

[bluebie]

Youre right, that is really busy and hard to tell with so much yellow splashed everywhere.

Thanks for the feedback, here's a pic rotated and without annotations.

Groups are numbered like

1   2   6   7

  5      10

3   4   8   9

Grr the forum editing my whitespace is killing me. Wish they had a 'preformatted text' option

 

[bluebie]

The smallest group with the lowest SD/ES? Just a guess...

They're all sub 1/2 MOA. Looks like it doesn't matter what the load is the rifle shoots lights out.

Yeah, wish I had a chronograph, those would be great data points to have.

 

[Fig]

As you progress you will find it's required gear, and it will tell you much more than groups @ 100 yds.

 

[bluebie]

As you progress you will find it's required gear, and it will tell you much more than groups @ 100 yds.

Yeah I totally agree with you. I'm not a benchrest shooter or anything. Current goal is to work up a load to be able to consistently hit sub-moa targets out to 600yds at local PPR matches. I think that once I burn out this barrel, I will probably get a chronograph and take a deeper dive into reloading to find further accuracy improvements.

Right now it's mostly for the money and time savings. You're probably laughing about that, but with all the taxes and shit in my county, I have to drive an hour each way to a store where I can even buy ammo, and it ends up costing me nearly $40 per box of eld-m. Chicago, for anyone wondering what kind of hellhole I live in

 

[Deleted member 113831]

Which bullet are you using?

 

[bluebie]

Which bullet are you using?

Hornady 140gr eld-m

 

[Deleted member 113831]

Hornady 140gr eld-m

#7 is likely to be your load. Adjust seating until it comes together.

 

[Sheldon N]

I like somewhere around #5 or just below. If my math is right that would be something like 41 - 41.2 range.

 

[AIAW]

Grr the forum editing my whitespace is killing me. Wish they had a 'preformatted text' option

It does. It's called "insert code". It will look like this in the toolbar:

 

[bluebie]

I like somewhere around #5 or just below. If my math is right that would be something like 41 - 41.2 range.

Yeah 41.2 is right. 40.9 and 41.5 on either side of it. This is the one I was leaning towards myself

 

[bluebie]

It does. It's called "insert code". It will look like this in the toolbar:

View attachment 7069436

Oh My
  It sure
    does.

Thanks man, TIL

 

[bluebie]

#7 is likely to be your load. Adjust seating until it comes together.

Are you basing this purely off the center of the groups? #6 is less than stellar as well.

 

[AIAW]

Oh My
  It sure
    does.

Thanks man, TIL

It's no VIM or NANO, but it works

 

[Deleted member 113831]

I like somewhere around #5 or just below. If my math is right that would be something like 41 - 41.2 range.

Loads 4,5,6 are very consistent, but they are also gonna be slow.

Shot #7 is where the POI starts to move. #7 and #8 are the highest POI's on the target (excepting #10 which was too hot), so the barrel is in an upswing and those two have similar distance from POA.

If my math is right #7 and #8 are 41.5 gr and 41.8 gr, which is the area where about 1,000 other OCW's have ended up with this bullet weight.

 

[Deleted member 113831]

Are you basing this purely off the center of the groups? #6 is less than stellar as well.

Yes. In an OCW group size is to be ignored. It means nothing. Seating depth brings the group together.

 

[bluebie]

Loads 4,5,6 are very consistent, but they are also gonna be slow.

Shot #7 is where the POI starts to move. #7 and #8 are the highest POI's on the target (excepting #10 which was too hot), so the barrel is in an upswing and those two have similar distance from POA.

If my math is right #7 and #8 are 41.5 gr and 41.8 gr, which is the area where about 1,000 other OCW's have ended up with this bullet weight.

Interesting observations about the POI shift. For some reason I hadn't correlated a shift up with an increase in velocity (duh). For the record, I did not include charge weights in hopes of not skewing the discussion, but since you guys are taking the time to figure them out anyway, I might as well post them for convenience

40.0
40.3
40.6
40.9
41.2
41.5
41.8
42.1
42.4
42.7

 

[Deleted member 113831]

Interesting observations about the POI shift. For some reason I hadn't correlated a shift up with an increase in velocity (duh).

The barrel moves up and down anyway, some much more than others. Yours isn't moving much.

But in a nutshell, barrel at the top of it's movement is better, barrel at the bottom of it's movement not as good. Barrel moving between is the worst.

Look up "positive compensation" if you want to know why.

 

[Deleted member 113831]

The barrel moves up and down anyway, some much more than others. Yours isn't moving much.

But in a nutshell, barrel at the top of it's movement is better, barrel at the bottom of it's movement not as good. Barrel moving between is the worst.

Look up "positive compensation" if you want to know why.

One more thing, you started getting sticky bolt at 42.7. That means the edge of pressure was probably around 42.4 gr.

The middle node is, in my experience, the most tunable node with acceptable velocity. I have a working theory that this node tends to show up in the area of (2%), or (2% + .2 grains) off of where you find pressure.

42.4 gr x .98 = 41.55 gr. That is right on your #6 (41.5 grains) load, and #7 (41.8 grains) is where your group started to move.

This theory has so far held true with multiple calibers from 223 up to 338 lapua and similar cartridges. The only caveat being that medium to heavy for caliber bullets are used, and the load density is 90% or better.

 

[_Raining]

Those group sizes are incorrect BTW. You need to set a reference in the app with the pencil looking icon. The red circles should be much closer to the actual hole size if you do it correctly.

 

[Doom]

If you overlay 4 and 5 you have a nice 6 shot group
with essentially the same POI. I would load between those and see how it holds up further out.

#7 looks like a scatter node. Its 41.8 and the node should be 1.5% below it or 41.2 which is where #5 is. The higher node woud then be 42.4.

My logic is based on Dan Newberry’s OCW method. It puts the nodes 3% apart and the OCW nodes 1.5% above or below the scatter node.

 

[bluebie]

Thanks so much everyone

 

[Deleted member 113831]

If I find a scatter node, and change the seating depth so that it groups....is it still a scatter node?

 

[bluebie]

If I find a scatter node, and change the seating depth so that it groups....is it still a scatter node?

An interesting question. But, if any load (within reason) can be tuned to group right by tuning the seating depth, why do we do any of this? I guess what I mean is that couldn't we just select the highest safe charge and screw with the seating depth until we get it right, and then just go shoot?

Then again, maybe that's where the lack of chronograph is holding me back. I'd guess you could go find the highest safe charge weight with the lowest sd/es and then tune the seating depth to make it group?

 

[Deleted member 113831]

An interesting question. But, if any load (within reason) can be tuned to group right by tuning the seating depth, why do we do any of this? I guess what I mean is that couldn't we just select the highest safe charge and screw with the seating depth until we get it right, and then just go shoot?

Then again, maybe that's where the lack of chronograph is holding me back. I'd guess you could go find the highest safe charge weight with the lowest sd/es and then tune the seating depth to make it group?

In my rather oblique way, I was disagreeing with the concept. I use OCW a lot. I trust it.

There are however, two aspects I can't abide. One is finding the OCW in relation to the scatter node. If you can change the shape of the group so dramatically, and you ARE going to change it when you do seating depth, how can it even be a useful reference?

The other is the round robin shooting. If your are shooting a benchrest rifle set up on a mechanical rest, I guess that it wouldn't be hard to be consistent. For the typical shooter with a field rifle and set up, the inconsistency introduced by constantly changing position is more variable than any difference in a few rounds worth of powder fouling.

 

[Fweedombypepe]

Those group sizes are incorrect BTW. You need to set a reference in the app with the pencil looking icon. The red circles should be much closer to the actual hole size if you do it correctly.

He's right. I use the same app and took me a while till I read the instructions on how to tell app a reference size.

OP @bluebie . theres a ruler? or pencil button in the app..figure out to use it. Oh and make sure the range is set right in the app too. Those groups are averaging closer to .75 then .2 I bet.

 

[bluebie]

He's right. I use the same app and took me a while till I read the instructions on how to tell app a reference size.

OP @bluebie . theres a ruler? or pencil button in the app..figure out to use it. Oh and make sure the range is set right in the app too. Those groups are averaging closer to .75 then .2 I bet.

Yeah for sure, thank you both for the tip. I didn't know about that aspect of the app. I'd figured it would calculate center-to-center distances based on the projectile diameter setting. Certainly not trying to embellish my fancy 3shot group sizes Ended up with a .63avg FWIW ?

 

[bluebie]

In my rather oblique way, I was disagreeing with the concept. I use OCW a lot. I trust it.

There are however, two aspects I can't abide. One is finding the OCW in relation to the scatter node. If you can change the shape of the group so dramatically, and you ARE going to change it when you do seating depth, how can it even be a useful reference?

The other is the round robin shooting. If your are shooting a benchrest rifle set up on a mechanical rest, I guess that it wouldn't be hard to be consistent. For the typical shooter with a field rifle and set up, the inconsistency introduced by constantly changing position is more variable than any difference in a few rounds worth of powder fouling.

I'm picking up what you're putting down. I thought the round robin method was very interesting, I loved and hated the idea at the same time. Anyway, given this info, and I pick a charge weight, how would you recommend to start modifying seating depth for a re-test? I'm sitting 0.010 off the lands right now. Do I start increasing the jump? In what increments? What is the suggested testing procedure specific to seating depth?

Edit: I should probably add that this COAL is at or very close to mag length

 

[Deleted member 113831]

I'm picking up what you're putting down. I thought the round robin method was very interesting, I loved and hated the idea at the same time. Anyway, given this info, and I pick a charge weight, how would you recommend to start modifying seating depth for a re-test? I'm sitting 0.010 off the lands right now. Do I start increasing the jump? In what increments? What is the suggested testing procedure specific to seating depth?

Edit: I should probably add that this COAL is at or very close to mag length

I use .005" jumps. I would start moving from your current length to shorter OAL's. I used to test a .040" spread, but found it to be unnecessary. A .025" spread will usually show you all you need to know.

The bore of the barrel will pulsate, for lack of a better term. It dilates and constricts. It does this in addition to whatever nodal movement is happening to the barrel as a whole. This is why you see the groups open up and then close again.

A .025" range of seating depth tuning will usually cover this entire cycle.

 

[Doom]

In my rather oblique way, I was disagreeing with the concept. I use OCW a lot. I trust it.

There are however, two aspects I can't abide. One is finding the OCW in relation to the scatter node. If you can change the shape of the group so dramatically, and you ARE going to change it when you do seating depth, how can it even be a useful reference?

The other is the round robin shooting. If your are shooting a benchrest rifle set up on a mechanical rest, I guess that it wouldn't be hard to be consistent. For the typical shooter with a field rifle and set up, the inconsistency introduced by constantly changing position is more variable than any difference in a few rounds worth of powder fouling.

I don’t shoot the 6.5 so I viewed the target with no knowledge of where the node might be. I have found that when you have a test that shows the type of consistancy that I see here, when you see a scatter like the one mentioned it often helps to identify where the node is likely to be. In this case I used it to pick 4 and 5 as opposed to 5 and 6. If you are correct about typically seeing the node around 41.8 then it warrants revisiting that area. As far as seating depth, experience has shown that you can tighten the groups up somtimes but the nodes typically don’t move.

I agree with your comment on round robin and fouling.

 

[bluebie]

I use .005" jumps. I would start moving from your current length to shorter OAL's. I used to test a .040" spread, but found it to be unnecessary. A .025" spread will usually show you all you need to know.

Cool, thanks. I'm thinking about doing 3x5-round groups of each seating depth from .010-.035 and running with whatever has the best average group size. Is that sane?

 

[Deleted member 113831]

I don’t shoot the 6.5 so I viewed the target with no knowledge of where the node might be. I have found that when you have a test that shows the type of consistancy that I see here, when you see a scatter like the one mentioned it often helps to identify where the node is likely to be. In this case I used it to pick 4 and 5 as opposed to 5 and 6. If you are correct about typically seeing the node around 41.8 then it warrants revisiting that area. As far as seating depth, experience has shown that you can tighten the groups up somtimes but the nodes typically don’t move.

I agree with your comment on round robin and fouling.

My comment wasn't meant to disparage you at all. I hope it wasn't taken that way. The OCW concept of paying attention to group centers is valid. It has been proven time and again. The whole "scatter node" thing I think, just muddies the waters. I wish Dan Newberry had left it out.

 

[Deleted member 113831]

Cool, thanks. I'm thinking about doing 3x5-round groups of each seating depth from .010-.035 and running with whatever has the best average group size. Is that sane?

That is what I would do.

 

[Doom]

My comment wasn't meant to disparage you at all. I hope it wasn't taken that way. The OCW concept of paying attention to group centers is valid. It has been proven time and again. The whole "scatter node" thing I think, just muddies the waters. I wish Dan Newberry had left it out.

No problem. Didn’t take it that way.

 

[bluebie]

That is what I would do.

?

 

[bluebie]

Just circling back to close the loop on this: I ended up going with 41.8gr of H4350. I tested 6 different seating depths and took the average of 3x 5shot groups for each. The best seating depth was the baseline configuration I started with at 0.010 off the lands. This came in at 0.62MOA, if I exclude my cold-bore first shot flier, it comes down to 0.42MOA. So, I'm going to run with that for now.

Thanks to everyone that chimed in to help me out with this.