Interpretation Help for Beanland OCW

[18Echo]

Can you guys help me interpret this OCW? They all look pretty similar to me....

I went and did an OCW test today for my Beanland .308 shorty with a 16.5" barrel.
I used Varget, and 168 Nosler Custom Comps inside of LC10 1xfired brass, and 210M.
These are 3 shot groups @ 100 yards.
Average Speeds were:
43.5 - 2572 ES-14 SD-7
43.9 - 2590 ES 60 SD 30
44.4 - 2610 ES 5 SD 3
44.8 - 2631 ES 6 SD 3
45.2 - 2657 ES 5 SD 3
45.6 - 2669 ES 21 SD 11
46.0 - 2695 ES 11 SD 6

 

[Twoboxer]

Tough call; the centers of all groups appear to be less than 1" apart lol. If I had the original targets for Ontarget, it might be clearer.

But I printed out your targets, adjusted a couple a tiny bit for distortion, eyeballed the center of each group, and plotted it. 43.9 and 44.4 turned out nearly identical, less than 0.1" horizontal (though the original targets may produce a different result using Ontarget software). Despite the high SD, I might go back into that area with 0.2gr groups.

Having said that, 46.0 is hard to ignore, not just because it's tight lol. It appears to be back in the rifle's comfort zone, and the charge is also ~3% higher than 43.9/44.2. If there were no pressure signs there, I might also try 45.8-46.4 in 0.2gr increments.

Nice shooting.

 

[18Echo]

Dan Newberry's website lists the 46.0 charge weight as an OCW for the 168. In my cases though that is really compressed and i have to seat them a couple times for the bullet to stay at its assigned ogive, and my bolt lift is a little sticky at the top, although it appears to be a good spot.

The high SD and ES for 43.9 might just be off weights in the charge, although they were all dispensed on a chargemaster.

 

[Dan Newberry]

I do like that 46 grain charge... if pressure is good, go with it.

 

[spoon063]

This is going to be a dumb question, and sorry to the OP for thread jacking for a second, but what are the "es" and "sd" numbers?

 

[Twoboxer]

This is going to be a dumb question, and sorry to the OP for thread jacking for a second, but what are the "es" and "sd" numbers?

ES = Extreme Spread . . . or the difference between the highest and the lowest speed (fps)

SD = Standard Deviation. In statistics and probability theory, standard deviation shows how much variation exists from the average or expected value. A low standard deviation indicates that the data points tend to be very close to the mean; high standard deviation indicates that the data points are spread out over a large range of values. Of little use on small sample sizes.

 

[Pinecone]

I would say your charge weight increments are bit large (over 1%).

And I would run it again, going up a bit more, as long as you are not getting pressure signs.

But 45.6/46.0 looks good. Also the 43.9 - 44.8 looks good, and is about 3% lower, so it likely your lower accuracy node.