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After decades of software development, training and use, I can tell you, unequivocally, there is no such thing as "idiot proof".
It is never as simple as. "...input velocity data."
Velocity data might be a piece of the puzzle but might be the least important piece. Just because you have a chronograph does not make that the most important part of reloading.
How about point of impact? How about pressure? How about OAL? How about case weight? There are so many others, too.
Many times, it is a process of looking at the relationship between, by linking, this factor with that factor that one sees what's going on. This is where Excel shines. It makes it easy to look at those relationships in a quantitative way.
"Hmmm,... what's going on THERE? That's not what I expected."
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I understand there are a lot of variables that aren't accounted for. What I am trying to figure out is how to record the variables that are worthwhile in the first stages of development. Everything cannot be accounted for and still be user friendly IMO.
As far as the pressure I record any signs in the notes section unless you are proposing measuring pressure somehow. POI shift is roughly accounted for by posting a picture of the target (assuming we aren't doing anything stupid like adjusting elevation between loads) of course you could use a program that measures the distance from POI and include that info if wanted and get better data. OAL is written into the data up top but would require a different setup to account for the effect of varying OAL... of course for me that usually comes after I settle on a charge, which is what I am trying to get to with this sheet. I have actually repeated the same sheet for a different OAL on a couple of occasions after finding promising combinations.
During load development, I would hope similar case weights are being used. Determining the effect of various case weights is simply a different exercise, no less valuable for sure, but this is further down the line from the initial load development. initially, I am going to do my best to remove that variable by using similar case weights or for plinking ammo at least the same headstamps. Additional sheets might be useful to capture the effects of case weight and OAL variation and shouldn't be hard to add.
The graph focuses on velocity because it is the most easily quantifiable over charge weights, and lends itself to graphing. That said it is NOT the deciding factor, for me that is a combination of group size, ES, SD, and making sure I am not in the middle of a significant POI shift between charges.
I want this to be as useful as possible, but I also don't want to let perfection become the enemy of progress. No single set of data will answer all questions, there is always more tweaking to be done in this hobby (temperatures, etc all change). But getting the most useful data for each load test is a worthwhile endeavor. I guess what I want is to figure out what people typically record when they grab their new load and sight in on the target.
-Mike