Ron AKA I read that article you posted by Mark Walker of Sierra and I think it's contradictory to what you've posted.
In the first results Mark posts the velocity readings alongside an image of bullet holes. Note how there is no reference aiming mark to measure vertical differences? (no Y axis to use in your graph example to compare velocity vs elevation because there is no point to measure from. Actually a person can’t graph the first results because the graphs x axis would be of powder charge against the y axis subjective interpretation of flatter horizontal results <<< no values to graph) Further Mark didn’t get a velocity reading for the last shot and didn’t seem to care. Mark found 3 consecutive increasing loads that were flat relative to one another and chose the middle. "When picking a load, I am looking for the most shots at the same vertical location on the target…” later in the same paragraph “I settled on 54.5 grains as the load I wanted to use. It’s right in the middle of the group so if the velocity goes up or down slightly, the bullet should still hit in the same place on the target.” This relates to the objectives of the OCW method doesn’t it? and no relationship drawn to velocity by Mark.
A person could graph the second results as seating depth vs group size but there are no velocity results to match are there? A person can’t say that all the results in the second example of 54.5 gn of 4831 would be the same velocity from the first example.
My points are this
- Mark draws the relationship of powder charge and seating depth to arrive at an accurate round.
- Mark uses the results on paper (subjective interpretation not measurable results to graph) to arrive at an accurate charge load, not velocity as suggested
- Velocity readings can tell you a whole bunch, but to use velocity to as the datum to develop accuracy from is like chasing a f%^t in the wind.
I’ll stick to what I posted earlier that the rifle has spoken on paper. Excluding pressure signs it can’t tell me anymore. After reading this article, a chrony result won’t trump the group that’s been produced.
I think you are missing the key statement in the article which is:
"It’s right in the middle of the group so
if the velocity goes up or down slightly, the bullet should still hit in the same place on the target."
It is all about velocity and elevation. You have to remember that the Ladder Test was developed before computers. And it may have been before chronographs became more affordable. The concept was to kind of draw a graph on the paper with your bullets. Some choose to keep moving the aim point (always at the same elevation) from left to right to spread things out a bit, like a graph. But the original test was to make a "ladder". Velocity always increase from shot to shot (at least it should), but you form "ladder rungs" when you hit a sweet spot where more velocity does not give more elevation. It is a matter of convenience how you do it. I prefer using a computer and graphing the results. Also keep in mind the Ladder Test works best with very accurate guns. With an accurate gun like the author of the article obviously has, the ladder rungs will become clear. If accuracy is not so good, then graphing the results and using more shots helps a lot.
In any case here is a graph of the results of this test plotted velocity vs elevation.
I believe this improves on the interpretation of the results. The author of the article picked a load from the range and decided that was the middle of the sweet spot. The graph would indicate that center of the sweet spot is closer to 2800 fps, than the actual load/velocity he picked.
The other thing this graph shows is that
velocity increases without producing an increase in elevation. That is the whole key and basis of the ladder test. An earlier article posted suggested that the sweet spot was when powder charge increased but velocity did not increase. That is totally wrong, and the graph clearly shows that.
The last advantage of using velocity is that it translates to other loads. For example if you were to switch the powder used, primer, bullets, or if the seating depth impacted velocity you could correct for it, and in this case return velocity to 2800 fps.
There is absolutely no contradictions between what I have posted and the content of that article. It is a perfect example of a ladder test.
