I have an operating theory that sweet spots most often show up at 2% off or 2% + 0.2 grains off of where you see pressure, somewhere in that immediate area. I have seen it time and time again. I have been scouring every single load workup I can find on the internet to gather data on that. I've mentioned it in a couple of other posts on here lately.
Well, in my personal rifles I've done it with 30-06 with 175's and 190's. With 308 I've done it with 2 different 175's. In 300 Winmag I've done it with 208's and 210's. I haven't taken the time to do it with 223 yet, but that is next.
Nothing about what I do is technically different than a standard OCW. I didn't re-invent the wheel.
Yes, which is in itself is nothing different than a standard OCW.
I would pick 27.2 with the 75's
That will work.
I do my OCW tests a little different than they were originally designed. I shoot each group without breaking position, then allow for cooling between groups. I opt not to do the "round robin" method. It has always worked for me. I've developed 28 loads for 19 different rifles/barrels since I started loading. I have always used the standard OCW targets. When I saw Skookum do them all on one line I thought it looked like a great idea. Much easier to read.
What makes 42.8 a scatter node as opposed to say, 42.6 or 42.2?
Not at the same time. Seating depths tested after the powder charge is found.
For the scatter node I look for randomness. 42.2 and 42.6 are kind of lined up. When I look for scatter I look for randomness. I use 5 shot groups too which makes it a lot easier to find. 42.8 on his target is the largest group that has no pattern to it. You won’t always get a clear scatter, especially with 3 shot groups but it’s another indicator that you can look for.
I don't really have a method, it's the OCW method. What does the original charge weight test look like? What method did you use to come up with the charge?
I’m not understanding how your starting OAL is any different that what I am doing. You have to start somewhere and it is always possible that the one you pick is not a good one and you need further testing. You said had you used “my” system and picked a 2.810 to start with you would have never found the magic load. Well you still would have been in the same boat had you picked that OAL to start with. What the heck does how I do things have to do with it?? It wouldn’t matter what system you were using. Had you started with 2.810 you could fill in the blank with any method and it would not change anything. How is what you did any less likely to not have you start with the wrong OAL? See what I mean? Picking 2.810 to start with was the danger, the method used is irrelevant in your scenario.
The order of operations is the key. If what you say is true, then the accuracy node being 1.5% from the scatter node would be a good way to confirm that you are in the right place once a winning OAL is chosen.
Still, you did charge weight first. What would have happened if you had chosen 8.210 as your OAL to do your initial 1 round charge weight test? How would that have turned out any differently than it would have if you were using an OCW as I do? It doesn’t make any sense that you are saying the way I do it would somehow be not as efficient as what you did because of OAL yet you still just picked a random OAL and went with it. There is no scientific way to guess at an OAL to begin a test. That’s it.
TO me scatter means absolutely random in relation to each other. The other two groups you cited are all lined up almost touching each other. That is not scattered. The one circled in red is as close to a scatter at it gets for that test. Hopefully that clears up that part.Maybe we are just talking past one another without understanding. I genuinely want to understand what you are saying and seeing. If you would, explain again please how you are defining the randomness you are seeing vs the lining up of the other charges.
Are you looking at group size, or shape or orientation to the point of aim? Here is the OP's target:
I see the pattern in the distance below the point of aim, and I see definite groupings in the angle from the point of aim. There are definite and recognizable patterns there. I can't see any discernible pattern in the size or shape of any of the groups.
What am I not seeing?
When I do an OCW test, I look at the pattern that the group centers produce. I completely ignore group size or shape. I ignore them because I know how drastically a small change in seating depth can change both size and shape. If I paid any attention at all to the group and I had chosen 2.810" as my starting OAL, then I never would have chosen that charge.
I am not using group size or shape to determine the winning charge. I am using size and shape to locate the scatter node and add another layer of data to consider, just as described in the OCW method. Still no rhyme or reason as to why the 1 shot test you did was somehow protected from a bad seating depth. Had you started at 2.810 the single shots you made would have moved. You can’t find a group center on one shot. The one shot is the center. As I said in my original post, the scatter node is just another indicator you can use to help line the data up. This was 100% true for the OPs test.
I'm still not sure what Skook is saying.
