OCW testing method for handloads

N

NChunter89

Member
This morning I decided to start working on loads for an AR chambered in 5.56 that I built a few months ago. After reading a lot about the OCW (optimal charge weight) method for determining the best powder charge I decided to give it a try. To make a long story short I ended up loading 3 rounds for each of the following powder charges of Varget: 24.6, 24.8, 25.0, 25.2, 25.4, 25.6, 25.8, and 26.0. The max charge for the Hodgdon and Sierra load data with the 69 gr MK was 26.0 and 26.1 respectively. I shot the 4 loads in a round-robin style like the OCW method recommends and the groups were terrible. Then I fired the last four charge weights the same way and here is a pic of the best target.



The best group was with the final charge weight of 26.0 gr. which is the max. It didn't show signs of pressure but it was a compressed load. So my question is, is it normal for the max charge to shoot the best? Most of my other rifles seem to like about middle of the road loadings.
 
I have a Browning A-Bolt and the hotter you load it the better it shoots. Some guns are just like that.
 
Not uncommon for warmer loads to shoot best, but each rifle/ammo is a study unto itself.

Personally, I like a full case of powder. Only shoot one compressed load, but it shoots well.

Regards,
hm
 
My 1:8 twist BCM likes 25.2 grains of Varget with 69 SMK and the tipped version. I've had several other loads (mainly Barnes bullets) that liked max charges.

One thing to remember about the OCW testing is that you're not necessarily looking for the best group of the test, but more a set of charges that all print in the same location on the target. Use the median charge of that group and play around with other factors to decrease the group size. My take is that the "Optimal" means the charge weight that can stand some small variations and still keep your zero.
 
NCHunter:

The maximum charge weight typically equates to 95-100% load density or nearly so and that is where the best accuracy often results.

Groups will almost always tighten as you approach max density as the pressure variation minimizes, and as a result velocity becomes more consistent i.e. lower standard deviation. It is all in the loading manuals...at least the older ones. The Lyman 47th edition is particularly good writing in this area with the formulas etc.
 
"maximum charge weight", check 5 manuals and you get 5 various answers. So, read the pressure signs on your cases. I stand the cases up in a loading block where I can see the base of the case for each load, and carefully examine the base with a magnifying loop.

Best loads are usually within 2.0g of a max load for that rifle, almost always.
 
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