This is my first outing with the 260 and I thought I’d share my results. I’m pretty happy as the worse load is still producing sub 3/4MOA accuracy.

Rifle: AIAT
Barrel: Bartlein blank, 26” long, work done by Mile High Shooting, little bastard gen2 break
Scope: Kahles Gen3 6-24

Load:
IMR 4451 from 39.3 to 42 gr
Lapua new brass
CCI BR2
147 gr ELD M seated with a 0.015 jump and an OAL of 2.870”

Target shot at 100Y, Robin style.

I think your 40.8 is a winner

Very nice.

40.8 gr looks good. I also look at the charges before and after, and they look pretty good as well.

Target shot at 100Y, Robin style.

I understand 100y, What is Robin style?

Looking good, Might want to stretch it out a bit more but 40.8 looks real good.

All groups are sub MOA which speaks well for rifle and shooter.

This is an OCW load dev test.

Robin style (round-robin), is when you don't shoot all the 3 bullets in a given load, one after the other.
In the above target, I shot 1 round with 39.3g, then one round with 39.6g, etc....the second round shot with 39.3gr was after shooting the first round of the 42gr load.

You can do some more reading on this here:

http://www.6mmbr.com/laddertest.html

Kevin1, thanks.

Would suggest moving back to 200 or 300 yards and the results will be obvious.

Also, a good load at 100 yards may not be good at 200 or 300.

Pick the best at that distance and then test out as far as it will be used.

I agree. I was testing some tweaking powder charges for my 7mm-08 yesterday. It was windy, so I merely shot 3 round groups at 100 yards, just to get a bead on things. Out of 5 charges, two got thrown out. But the good ones measured .50", .80", and .55". I'll go back and re-shoot those at 200 or 300 yards, for 5 shot groups.

Yes, yesterday was pretty windy.

But guys, this is an OCW test. It's not meant to test the accuracy of the load. It's to identify a load charge that will minimize the vertical dispersion in warmer/colder weather. That's a huge deal for long range. After that, you can play with the seating depth to increase your accuracy.

From that aspect, that 40.8gr looks good, but so does the 41.7gr charge.

Below the vertical variation of the point of impact in reference to the point of aim.



Gr ------ Vertical
39.3 ------ 1.68
39.6 ------ 1.42
39.9 ------ 1.7
40.2 ------ 1.41
40.5 ------ 1.47
40.8 ------ 1.38
41.1 ------ 1.09
41.4 ------ 1.14
41.7 ------ 0.89
42 ------- 0.83

But, OCW does not tell you anything at 100 yards. That's why it's done at 500+ yards. The 40.8 does look good, but it will be slow for a 260 Rem. Any chronograph data?

Also, why does the vertical variation of the point of impact in reference to the point of aim matter? As your powder charge goes up, so does your speed, and the group impacts higher on the target.

If I'm trying to find a long range load, I'm testing at minimum 200 yards, and prefer 300 on a calm day.

So, you have fired 30 shots for testing. What did this tell you? And what's your next step(s)? I'm just trying to get an idea on your process.

You're mixing up ladder test (done at longer range) and OCW (done at 100Y).

Next step? Load up some rounds with 41.8 gr of powder, do some chrono measures, and hit steel from 900Y to 1100Y.

I am far from an expert on this subject, the below is just my understanding of the procedure I reference below. I'm interested in hearing what some of the more experienced people here have to say about it.

I tried using this OCW process using the instructions I found here: http://www.ocwreloading.com/about.html to develop a load for a 6.5 creedmoor and a 30-06.

It got my interest based on the following claims:
- Determine OCW with minimal number of rounds
- Improved (less) temperature sensitivity
- 100y shooting range (10 minutes away)

So after reading the manual several times, I decided to "trust the process", load some ammo and go to the range. I did the 6.5 creedmoor first, 129 nosler ABLR, H4350. After the first trip to the range, I came home with a pattern of targets that looked similar to yours. My conclusion was that I didn't go to a high enough charge weight (I don't know what the max is for your powder/bullet combo). So, I loaded a whole new batch up to a higher charge weight and went back to the range. After shooting, the results looked more complete, and chose what appeared to be the OCW according to the process, and then started to adjust seating depth using the charge weight I had identified.

Getting the right seating depth took a while, but I was finally able to make 3 holes touch on rounds 96, 97, and 98... (fired round robin)

I wasn't impressed with how many rounds it took, but part of that can surely be contributed to my lack of experience...
As for the temperature stability claims, I loaded these in Feb, and still have about 40 rounds to try out this summer. We will see...
Going to longer range, I have a 16" plate at the deer lease that I was able hit 3/3 at 600y (~2.7 MOA) I know that's not outstanding proof, but ya gotta work with what you got sometimes...

After going thru the same process for the 30-06. I came to the conclusion that I need to order some Lapua brass... and/or get an annealing machine, the brass was work hardening fast, believe it was giving me neck tension problems.

That being said, if I were to "trust the process" with the data you've given, it looks like either 40.5, 42. Not sure what the max is, but it would be interesting to see where 42.3 would end up?

I like charts, so I plotted the data you provided, so it's easier (for me at least) to see where the "flat" spots are.

Like I said at the beginning, I am not an expert at this, and this was just my interpretation of "the process" I would like to hear from others here if there is any merit to this process? Or was I just drinking the cool-aid?

I guess I'm confused about OCW... If it is meant to find the load that will "minimize the vertical dispersion in warmer/colder weather", wouldn't you have to shoot in both warmer and colder weather? P_102

Oh no you didn't.

Use whatever method with whatever name, but try it at least at 200 yards and the results will be clearer and more useful. 300 yards is even better if wind is not too much of a factor.

Take the best load from 200 or 300 yards, check it at 500 or 600, and then stretch it out to 1,000.

I've seen loads that were great at 500 yards that were not particularly good at 1,000, but every load the was good at 500 also was good at 100.

Also, banging steel is fun, but paper targets will provide more precise information for load development, and also provide a good place to take notes for future reference.

OCW, ladder test, sure, it's not methods I use. My point is, doing this test for a long range rifle at 100 yards with no chronograph only gets you partially to your goal. You need longer distances and chrono data, unless you don't care about the speed.

Also, why does the vertical variation of the point of impact in reference to the point of aim matter? As your powder charge goes up, so does your speed, and the group impacts higher on the target.

This what I don't get. After reading the article it's essentially trying to accomplish a ladder type test at 100yds and more rounds fired. According to the linked article you look for loads that are spaced a similar distance from the poa which should show you a node.

yup, once you find a node, you can throw in a little more of less power and you POI won't change that much (therefore if it gets hotter/colder you're POI won't change much).

Sigmund,
You're correct, I should probably have gone above 42. But this is a 26" barrel and I thought I don't need push it beyond 42gr with a 147gr bullet (even if no pressure sing). I do have several accuracy nodes, but I'm going with 41.8 to get higher MV and you can see clearly a node between 41.7 and 42 (and probably a little above 42).

If my chrono numbers (AV/ES/SD) are not satisfactory, I'll make some changes and probably go above 42gr. But I'm confident that everything will be fine.

Kevin1, I would be doing my work between 39.6 and 40.8. Particularly 40.8. It is summer and that is the top edge of what appears to be a 1.2 grain node. Plenty of room below to accommodate velocity loss in cooler weather. You have enough space over the top to not be worried about pressure. If I were in your shoes and wanted a load I could stretch out, I would check to see how consistent velocities at 40.8 are, then stretch it out if the velocity checked out. Your poi was pretty constant for those four loads. When you lose some fps in the winter you zero should hold up. That's what I look for in a solid load.

Because you have shot such a wide range compared to the load weight, you should have 3 different nodes in the data. Finding the "scatter node" in some case is more important than finding the accuracy nodes(straight from DAN). Dan Newberry and Chris long came up with OCW independently of each other. Below is the link to dan's page. Listening to a reloading podcast where dan talked was way more informative.

The nodes look to be at 39.3, 40.5 and 41.7, even though 40.8 looks great.

http://optimalchargeweight.embarqspace.com/

If you are serious about ocw I would try to find Dan' podcast. In the little development i have done, once I find one node I can predict other nodes.

You hit it on the nail!! That's exactly why I went with 41.7 (well....41.8 as I did a little extrapolation).

Loaded some rounds with 41.8 gr and shot the below targets
5 shot groups:
100Y : 0.476”
300Y: 2.028” and 2.139”

It’s just ok. I need to play with the seating depth to improve the accuracy.

The chrono for 5 shots:
Average 2695
Hi 2703
Low 2684
Sd 7
ES 19

The first shot was by far the slowest (2684) and that’s what is messing up the ES. The speed is exactly where I want it to be.

Kev1,

Once I "find" my node, I shoot a couple tenth of grains above and below to be sure I hit center of the node. Af On the second trip. I will reshoot the node against the above and below charge at 100 yards. But I will also have some rounds of the node to shoot at 500 and/ or farther.

After I am sure of the node, I play with the depth.

Goood luck and keep us posted.

This discussion has my OCD going...

I've read all of the referenced links several times over the last few months. The thing I can't seem to fully understand/identify is this "scatter node".

Kevin/scdogman,
On the original target posted, which would you identify as the scatter node and why? I just can't see one that stands out...

When I was trying to do this I had to make a chart similar to the one I posted earlier to find the areas where the slope of the line flattened out (like it did between 40.2 and 40.8) to identify the nodes.

That was why I was interested in what 42.3 would have done, if it would have made the line come up slightly, that would have put 42 about at the center of that node. I would have been to OCD to not shoot the whole test over up to 42.3... which is no small part of why it took me so many rounds to get what I ended up with...