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OCW Results - how would you read this?

SMTGWKD

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Minuteman
Mar 3, 2017
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Watched YouTube videos from Bangsteel Long Range Shooting School and thought I'd play a bit as I have two new loads to work up.

Rifle is 2A Xanthos 20" CF Proof with JP internals shooting 140ELDs over H4350 from 41.0-41.5 grains. All groups are 4 shots.

Result are pictured. I shot round robin style and only f-d up one target where I accidentally shot off target and had to overlay :)

My thoughts:
1. Scatter node at 41.5 grains?
2. Guy in the vid says optimal charge is 1.5% from scatter - in this case that would be the 41.0 charge and it grouped into nearly one hole after my clean bore shot (scrubbed the barrel last night).
3. Super interesting that velocity is nearly flat across the loads. Maybe 41.0 is a full burn in a 20" barrel?

Let me know your thoughts!
 

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You couldn't tell much from that test, the window is not big enough. Besides that your POI is consistent from 41.0-41.5 which is what one would expect if they were in a node. What brass? 41.5 with a 140, in Hornady brass is pretty well known load. I generally just load that with a seating depth test anymore. If you have thicker brass like Lapua, its going to be different.
 
Hornady Brass - reason for rechecking is some inconsistent accuracy out of the 41.5 load I have piled up (about 100 loaded rounds left). Was interesting to see this data.
 
It difficult to tell much since your targets don’t show a clear point of aim. In the OCW test consistency in POI is the major point of evaluation. Typically OCW is done with three shot groups.

What COL/CBTO did you use?

The scatter at 41.5 does point to a node around 40.9 and 42.1 grains. I don’t shoot the CM but if 41.5 is a known node or load then I would shoot this test again from 40.5 to 42 in 0.3 grain increments.
 
Thanks - valuable input. POI is messed up on one target (41.4) as I decided to change my reticle point of impact closer to the point of aim by .6 mils. Rookie decision. The others are accurate.

I'll run again today as I'm enjoying learning how to become more efficient developing a load to go shoot - steel and animals are the fun stuff.
 
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Here's today's run based on Doom's advice above. Really disappointed that my Labradar data got jacked as there was another guy shooting an AR10 Creedmoor and a few of his shots ended up in my strings. Only know a couple of single velocities as a result - no idea where the rest belong. Lame.

I have my own assumptions from the last test coupled with this one, but very interested in more experienced insight. Love to learn.

How would you read this?
20220205_210124.jpg
 
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I would be looking between 41.1 and 41.7. The POIs are all about the same. Having some knowledge that 41.5 is a known load I might pick that instead of 41.4 and play with seating depth to try and tighten it up. That sold out you in the 2630 fps range. Don’t get too sidetracked at this point by group size.

OCW was a load development method that Dan Newberry devised and it did not depend on chronograph data. I would recommend not using it for at least two reasons. First is that three shot data is pretty much useless except to give an idea of what the average velocity is going to be. The second reason is it is a distraction. Granted a LabRadar is usually less of one than others.
 
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Thank you - I shot this group at 41.5 as well yesterday just to test the known node. Since I want shooting a long string, the chronograph data logged reliably.

This is the step where I typically start chasing my tail.

When you say "looking between 41.1 and 41.7" - without a well-known node at 41.5, what would be your process here to look between those points?

Really appreciate it!
 
I would have picked 41.4 as being centered between 41.1 and 41.7. OCW is about finding a load that is not overly sensitive to charge weight that shoots to the same POI for variations in components and charge. In this case you start at the center. You can refine the seating depth to tighten up the groups.

A few months ago I wanted to verify a load that I use in LC brass (43 gr) with a change to Lapua. I pulled one shot on the 43.2 so it’s not included. If you overlay the 43 to 43.4 shots into one 8 shot group, what would you think of it?

Obviously, once you refine the load you have to check it at distance.

Also, once you get in this node you can play with the chronograph to optimize your SD.
160BE5D1-B0F0-41F7-A737-1F7960FF5401.jpeg
 
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Thank you - very helpful response.

Is there a particular charge weight spread as a percentage that should be bracketed or simply find the spread that hits similar poi and load up in the middle to maximize load forgiveness?

Example - is the same poi occurs across a .3 grain spread - but changes above/below - load to the middle of those and test?

Thanks again!
 
It depends to some extent. Usually I‘ll pick in the middle, 43.2 in the case above. This is a node that I know and was looking for any change due to the case change which I thought would be .1 grain. But it looks like .2.

I used 0.2 gr increments since I knew this was the area to be in. Normally in 308 sized cases you would run 0.3gr. When you find the center then you can tighten up around it if you wish. Hopefully you find three loads but sometimes it’s only two. When that happens you can work in between or just take the average of the two and work with it.

You mentioned the 1.5% from the scatter node. Typically the nodes are ~3% apart, but I have seen a few cases where there is a node where the scatter node should be. Can’t explain it. When using lower capacity cases like 223 the nodes are only about 0.7 grs apart so the nodes are typicality only 0.2 to 0.3 grs wide.
 
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