Load development method : Optimal Charge Weight

todbartell said:
I just question that nodes exist, I won't say they don't exist - the testing to prove that would be never ending

I pick a bullet I want to use, knock about 5% off the max load and load up ten rounds each with a few different powders (anywhere from 3 to 10 types). Seating depth will be at least .030 off lands, .050 off for monometals (or as long as mag lengths allow)

I'll fire the loads, in 3-5 round strings depending on barrel contour and intended use (hunting vs target) at 200 meters. Ending up with ten round group, which is measured for group size, mean radius. I will adjust the charge weight up or down, depending on what I am looking for. I'll retest the best results with 15 round groups, eventually what works the best will rise to the top
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Well you could reverse engineer to find out.
Take your good 10 round choice and compare it to a slightly different powder charge on either side. Shoot at 200 or farther. When I fine tune powder it’s only in one tenth steps.

Then you can also compare seating depth in the same way. I rough test in 3 thousand’s and fine tune in one thousand’s steps on either side.
 
Lead hammer said:
Well you could reverse engineer to find out.
Take your good 10 round choice and compare it to a slightly different powder charge on either side. Shoot at 200 or farther. When I fine tune powder it’s only in one tenth steps.

Then you can also compare seating depth in the same way. I rough test in 3 thousand’s and fine tune in one thousand’s steps on either side.
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This is where the round counts stack up big time in load development. If you do it in ten round groups, which are much more statistically valid samples than 3 or 5 shots, testing powder charge steps of 0.1gr, you'd fire off 70 rounds right there (base line 26.10grs, testing 26.0, 25.9, 25.8 & 26.2, 26.3, 26.4grs) - now we find 25.9grs gave the best group size and/or mean radius. Now testing seating depths, going from the base line 1.892" CBTO, we test .003/.006/.009/.012 shorter, and longer - for 90 rounds of test loads, bringing load fine tuning round count to 160 rounds

Finer seating depth tuning of .001 on either side of the best jump from the first test, brings load development fine tune round testing to 180 rounds

On ten shot samples of the exact same load, you'll see variations of results of 30-40% smaller, and 30-40% larger from the average. If a guy did super in depth testing, resulted in an average 0.75moa ten shot group, you could fire a bunch more with the exact same ammo and see groups from 0.5moa to 1.0moa

3 shot samples vary 60-70%, which gives us the "node" results on target. 0.5moa average group will print results from .18 (node!) to 0.83moa with the exact same ammo.

So do nodes exist? I hope to get out later today and do my seating depth test for OCW 2.0 to shed a bit more info on this load development technique

Silverado said:
How did you settle on 34thou off the lands?
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It put .224" of bullet shank below the case mouth. I generally don't like to seat bullets closer to the lands than .030 anyway, so it worked out. SAAMI 223 Rem overall length is 2.260", these test loads were loaded at 2.291"
 
I was talking about 10 round groups on either side when you think you are done with your load to confirm.

F class shooters hope for 5” groups at 1000. They do not shoot their barrels out with mega round load development. Yet they somehow manage to be close. They don’t get hung up with stats. We should not be hung up on it either.
 

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todbartell said:
Dan Newberry's OCW
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OCW 2.0
Howa 1500 Carbon barrel / MDT XRS chassis ~ 24" barrel 6.5 Creedmoor
130gr Sierra Tipped Matchking
Winchester 760 ball powder
Alpha brass / Remington 9.5 primer
.056" off lands

Od3IBqR.jpeg


Loaded from 41.80 to 42.80grs in 0.2gr increments

100 meter target

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42.4, 42.6 & 42.8grs were the three consecutive charge weights with the least variation in impact location , so I picked 42.60grs as my optimal charge weight

41.8, 42.0 & 42.2 had the biggest variation, so I picked 42.00grs as ANTI NODE

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On a previous OCW test, it was brought to my attention that I failed to to an optimal seating depth test! So I loaded up 42.6grs OCW and adjusted seating depth deeper by 003" , .006" and .009", and further out by the same .003, .006 and .009 - the internet tells me that small increments are best as you don't want to skip over a node

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2.224 - 0.86moa 3 shot group
2.227 - 0.74moa
2.230 - 1.21moa
2.233 - 0.27moa
2.236 - 0.76moa
2.239 - 0.55moa
2.242 - 0.20moa

I decided 2.240" CBTO woud be optimal seating depth, as the groups of 2.239 and 2.242 were both excellent and shared the most similar point of impact for 2 consecutive depths. Also picked 2.240 as it will stay in tune longer then 2.241"

The worst seating depth should be 2.230" CBTO due to the erratic 1.21moa test result

I loaded 28 rounds at 42.60grs (OCW) with a CBTO of 2.240", and 30 rounds at 42.00grs with a CBTO of 2.230" (ANTI NODE!) and shot them at 324 yards in calm conditions. Fired 5 shots, letting it cool, repeat





The results :

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42.60grs OCW / OSD : 2837 fps, SD12, ES51
1.73moa 28 round group @ 324y
Mean radius 0.37moa

&

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42.00grs Antinode : 2785 fps, SD14, ES65
1.50moa 30 round group @ 324y
Mean radius 0.35moa










 
Bravo sir todbartell!
This is a great contribution to our knowledge.

May I suggest H4350 powder and CCI 450 primers as the next test? Especially to see if the ES/SD numbers improve.

Another interesting test would be to shoot a well-regarded bullet, like a Berger 140 LRHT hybrid.
 
My current load development method involves loading until pressure or velocity goals/limits are reached with 3-shot groups.

Then do 2x 10-shot groups. One at near pressure and one with ~1gr less.

If the accuracy or SD isn't good enough for you, then switch bullet or powder.

Use GRT or quickload to find a case fill that is 90%+ that also burns 95+%

velocity nodes aren't real. there is a non-linear relationship between powder charge and velocity as you approach a full case (and other contributing factors) IMO.
 
boxhitch said:
Isn't Quickload all about nodes? I've never used it, only seen many of your past posts with data from the software
or is QL just another way to get there?
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Quickload is a predictive tool, think of it as custom / tuneable load data for YOUR rifle. QL software doesn't suggest accuracy nodes
 
I appreciate the work and money spent.
I don’t think you were done.
42.4 is 1/2” to the right of 42.6.
42.6 is 1/2” higher than 42.4. I don’t think you are in your OCW yet.
In fact, 41.8 and 42.0 are impacting at the same location despite the vertical strings, but we don’t know if 42.1 is friendly or not either.

42.6 and 42.8 are friends but don’t know about 42.5, is that friendly or are you on the edge of a “node “ and I would have tested to 43 if it was safe.
 
So far for me it’s two OCW’s then usually one OSD. From there it’s colored bullets at 300M. I would like to get to only colored bullets at 300, but I’m not that confident in beginning there yet.
 
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