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Old August 24th, 2019, 12:29 PM #1
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Unclear OCW

I do OCW load development not “smallest groups”. Normally, the OCW is easy to spot and cross check confirmed by a scatter node about 3% after accuracy node. Until today.

I’m trying 168gr Sierra matchking bullets and started off with a low end load for making sure I was close enough. I didn’t want to CHANGE zero at this time. Was happy enough but turned out to also be the smallest group of you exclude the cold bore shot hahah.

I... think I’m going to settle on 75.4gr splitting 75.2 and 75.6 gr. If you do OCW dnd see something I don’t... please share and clue me in??




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Old August 25th, 2019, 12:10 AM #2
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74, 74,4 and 74,8 are all about 3 squares left and 2 squares up.

If you shot these properly round robin, I would say 74.4.

Also 73.2 and 73.6 are about the same location, and 73.4 is about 3% lower charge than 74.4
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Old August 25th, 2019, 07:48 AM #3
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Unclear OCW

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Originally Posted by Pinecone View Post
74, 74,4 and 74,8 are all about 3 squares left and 2 squares up.

If you shot these properly round robin, I would say 74.4.

Also 73.2 and 73.6 are about the same location, and 73.4 is about 3% lower charge than 74.4

I see what your saying. The part that threw me off was the 74,74.4 group sizes. I tried to look at submoa groups with same POI and that threw me off. I might do those again. Or just go with the lower charge.

Normally it’s accuracy node, 3% higher is a scatter node (which could just be s dramatic shift in POI), another 3% is another accuracy node. It’s much easier to tell with a 223 but I’m struggling with this.


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Old August 25th, 2019, 09:30 AM #4
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No, 3% from accuracy node to accuracy node or scatter node to scatter node. 1.5% between accuracy node and scatter node.

You are looking at similar POI, NOT group size.

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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.
Group size will shrink when you start working on seating depth.

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Remember, don't get "bowled over" by a tiny group which falls outside the OCW zone. You can tune any of the groups to be tiny with bullet seating depth changes.
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Old August 25th, 2019, 10:44 AM #5
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Ahhh yes. Okay. I was using the group in combination of POI as a requirement. I saw the part about fine tuning but saw it as that: “fine tuning” an already submoa group part of the OCW.




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Old August 25th, 2019, 11:56 AM #6
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Quote:
Originally Posted by Pinecone View Post
No, 3% from accuracy node to accuracy node or scatter node to scatter node. 1.5% between accuracy node and scatter node.

You are looking at similar POI, NOT group size.



Group size will shrink when you start working on seating depth.
Pinecone
What is current thinking on seating depths. I used to seat bullets to touch lands, then back off perhaps 1/2 a turn to get best groups. Obviously actually touching the lands could cause pressure spikes with poor results. I realize that can change a bit from rifle to rifle but that seened typical when I was doing benchrest back in the 80s to earky 90s. I don't know what most are doing these days.
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Old August 25th, 2019, 12:37 PM #7
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I am new to load development myself. I found adding velocities using this method and OCW actually helps.
https://www.65guys.com/load-development-part-1-of-2/

Using the combination, I was able to develop loads for my 6.5 CM that I can consistently hit 1000 yd targets with.
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Old August 25th, 2019, 03:02 PM #8
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Quote:
Originally Posted by dbledoc View Post
I am new to load development myself. I found adding velocities using this method and OCW actually helps.
https://www.65guys.com/load-development-part-1-of-2/

Using the combination, I was able to develop loads for my 6.5 CM that I can consistently hit 1000 yd targets with.
Wow, bizarre. I had never visited that site or heard of this method before today but somehow stumbled across the same information about 15 minutes ago in what appears to be a different article. Looks interesting.

http://www.65guys.com/10-round-load-...t-ladder-test/
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Old August 25th, 2019, 03:02 PM #9
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Plenty of wiggle room there for me on seating depth. I’ll play around and see what I come up with.

Any thoughts on seating depth distance changes? As in 0.02 off lands, 0.03 4... etc etc. what “step” is a good step for changing seating depth for testing if “right off lands” isn’t great. Chuck it away or try another depth...?


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Old August 25th, 2019, 04:04 PM #10
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Sierras usually like to jump, start at .020 off lands. I usually go in increments of .003 and only load 2 rounds max. You will see the group opening and close as you progress.

Each chamber is different, I've seen guys go as far as .050 off, but chamber was cut to .120 freebore in a 6x47.
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