I see the term “node” used a lot, and I don’t know or understand what that is.
@South Prairie Jim has a few pictures he can post here, or which can be seen in his Long Range Load Development thread which depict Audette Ladder tests and very clear nodes resulting from them. In that test, the node is identified as groups of charge weights which all have the same or similar vertical points of impact, relative to one another.
The Newberry OCW test - which is how SPJ is evaluating your target above - also defines nodes by adjacent charge weights which all impact at the same vertical location (relative to separate points of aim) compared to one another.
As an example: here’s a Newberry test I evaluated for a shooter on another forum several years ago. Analyzing these targets, we can see there is some variability in vertical position of the group from one charge weight to the next at the left end, then between loads 5-6, the vertical position flatlines, and then starts to rise again from 6 to 7 to 8. Somewhere between 4 and 7 is the center of a “node.” This means the load there is very forgiving of errors - a little variability in neck tension or charge weight, primer power, case capacity, bullet weight, etc will not be as influential on the point of impact for those bullets as it would be for a load at the left, outside of the node.
Projecting these bullet holes onto the same target, we would have an Audette Ladder test. The same analysis is done - we look for adjacent charge weights which cluster around the same vertical position. Again, we see a node in the 5-6 ballpark where the adjacent charges have nearly the same vertical position, so we’d test again in this area to confirm the edges and center of this node.
Another proven load development method is the Satterlee Velocity Curve method. In this test, we eliminate the challenges of mechanical and environmental influences on our group sizes and bullet POI’s and focus on the velocity. In this test, again, we’re looking for adjacent charge weights which are relatively the same, meaning increasing charge weight doesn’t increase velocity over a couple or a few charge weights. This example actually includes 3 nodes, one at the bottom, one at the top, and one in the middle. We can see a window at 41.6-41.8 where those 6 shots only varied by 7 fps, and the standard deviation was only 2.4fps. Which is tighter than MOST ammo would offer even if all of the charge weights were the same, let alone half and half loaded at 0.2grn apart. So in that test, loading at 41.7grn meant I could get the same velocity despite an error in powder charge accuracy up or down by at least 0.1grn, reducing my vertical dispersion downrange, compared to the same error, say, if I loaded at 42.0, where an error 0.1 up vs 0.1 down might mean ~30fps difference, promoting up to ~6” of extra vertical dispersion at 1000yrds. So I load “in the node” at 41.7 instead of 42.0.
I guess some want all in one hole.
