OCW readings

[chrisxj]

Ok i did a OCW string and i dont understand the outcome other than i dont think my rifle likes 4451 other than 2 of the groups so maybe someone can read the magic ball for me.

243 105 amax

[hereinaz]

Step one: find and mark the center of each indiviual group. Call that the Group POI.

Step two: ignore the actual bullet holes from here on out and only focus on Group POI points.

Step three: find the three Group POI point that are closest together.

That is the purpose of OCI, because now you know that if you load at the center charge, if your scale is off a little bit, or the temperature is higher or lower, your POI will change the least.

Once you get the charge node... then start with seating depth.

[hereinaz]

My first OCW test was similar, but I followed protocol.

I was shooting Berger, so I followed their recommendation for testing jump/loading length.

Sure enough, I increased the jump, and then shot a group at 200 yards that was smaller than my best load at 100 at the OCW.

Find an Optimal Charge Weight, and then work on OAL/jump. It was like magic when it all came together.

[hereinaz]

Starting from the left, I would say your number 4, 5 and 6 were the node. See how the center of each group is so close?

The last load jumped higher, and the others were moving from low to high, until they stabilized the most between 4, 5 and 6.

Pick load number 5 and you will have a very consistent load at multiple pressures, and many things can affect pressures, from heat to case capacity inconsistency, different lots of powder, variations in charges, etc.

You may not shoot bugholes, but you will have a very reliable load. But, you could.

My OCW was alot like yours, then I shot this at 200 yards with my 7mm rem mag. https://uploads.tapatalk-cdn.com/20170409/2a240d905edeee17450924c815d1c644.jpg

[chrisxj]

Yea i hear ya but iv been tryin to rap my head around this for a while now im gettin it little by little.I see what your sayin with 4,5,6 they look the most uniform and at pretty much the same elevation wise.Like i said im still tryin to get head around this concept

[chrisxj]

but what about 2,3 they are all close to see thats what i dont under stand. Not to brag but when they made my barrel they they must of put some good magic in it because by all means thats not a great group but its still moa i have a pet load with 7828 that will print bug holes. But ive noticed that no matter what powder i use i will allways get MOA with and that allways screws with me to.

[Deadshot2]

I may be the "odd man out" but when I get OCW results like the OP's I usually work with "load #2". Almost every shot is on the same horizontal plane indicating that the speed is most likely the same. Horizontal spread is easy to get from improper shooter input like trigger pull/grip, or rear support.

My issue with three shot groups is that one shot that doesn't join the other two can be from several causes and shooters are all to quick to condemn the charge weight because it doesn't fit the formula. I prefer 5 shot groups. That said I don't do OCW tests until I've shot a Ladder test at 300 or more yards. I already know where my rifle's nodes are so all I'm really doing is refining the charge weight and seating depth.

I then end up with this more often than not

https://im1.shutterfly.com/ng/services/mediarender/THISLIFE/004053667850/media/32831748937/medium/1490746025/enhance









For the record, that's a 15 shot group at 100 Y that measures .490 MOA with an Average to Center of .082 MOA. There USED to be a small circle with an "X" in it on the target before shooting this group.

[hereinaz]

The ocw test is not I repeat not testing accuracy of any one individual group. It is testing the overall accuracy of a series of charges. You are looking for the optimal charge and I repeat the optimal charge and that is why you want one charge that is stable even if you go up or down a few grains. You want the point of impact to be in the same place even if there's a little more pressure or a little less pressure.

[hereinaz]

The ocw test checks how the variation of pressure due to an increased or decreased charge effects the point of impact.

I would say on my limited knowledge and limited experience with interpretation, that your optimal charge is going to be around the 5th one, because even if you go up or down from that charge the point of impact moves the least.

I don't have a lot of experience interpreting the ocw test, but I am just applying the principles to what I can see. Maybe others can read the tea leaves better than me.