08-15-2022, 11:30 AM
I have to go with Klem on this one, in the main. The biggest operative imo for curve deviations in a single-shot ladder is the normal distribution occurring at each shot load. At the top end, looking at the curve just above here, I would say the charge is getting compressed causing powder ignition/burn to vary and a resulting slower exit MV -- either that or again, distribution-variation of MV at that charge.
Now I do use a single shot ladder to begin most of my load developments but don't think for a minute that 10 shots will tell me the whole accuracy story for my barrel and the powder/bullet/primer/brass story. Rather this string establishes the overall powder curve response for my specific barrel to the combo particulars.
I graph my results and then, to weed out at least some of the distribution deviations, will curve fit the powder response along with the curve of "book" powder for comparison. The slopes of the 2 curves should be close to each other even though the curves will differ on actual MVs... This then tells me where I want to concentrate development to find the nodes. Overall it takes me somewhere 30-50 rounds to identify my desired load.
Primer type, powder lot, barrel length (vs "book length"), internal friction characteristics, brass differences, plus more variables, some controllable, some not - you work with what you have.
I would find it highly unlikely (well nigh impossible) to ever see a completely linear (in Klem's terms, elastic) powder-MV graph due to all the variables plus some measuring uncertainties. I'm not a benchrest shooter nor as good a shooter as some of you guys but the physics and mechanics of the internal ballistics, coupled with all the uncertainties which are never quantified, these all militate against thinking you will find your perfect load in 10 shots.
ps one other thing going unmentioned, and this is just a theory of my own, is that premium barrels will probably show less distribution/variations than rack grade if only b/c they have a much more premium, controlled and quality-oriented production rigor. But that's just a theory of mine. Satterlee's stuff could also be making advantage of this effect as he is concentrating on prs/1000-yd matches, those guys don't use the rack grades we oft-times have.
I would venture to say that if any 10-shot string were repeated under similar, controlled circumstances at close-to-same-shotcount (for barrel internal similarities), you would see an oscillating string with different peaks/valleys from the first string you shot. Hopefully they would overlap each other... and theoretically, after several of these overlapping strings, the wide-varying MV's/powder charges and the narrow-varying MVs/powder charges (ie, "nodes") would become evident. I have yet to see anyone do this several-string test and have yet to see the graphs/data, but mechanically that's what I would expect.
Now I do use a single shot ladder to begin most of my load developments but don't think for a minute that 10 shots will tell me the whole accuracy story for my barrel and the powder/bullet/primer/brass story. Rather this string establishes the overall powder curve response for my specific barrel to the combo particulars.
I graph my results and then, to weed out at least some of the distribution deviations, will curve fit the powder response along with the curve of "book" powder for comparison. The slopes of the 2 curves should be close to each other even though the curves will differ on actual MVs... This then tells me where I want to concentrate development to find the nodes. Overall it takes me somewhere 30-50 rounds to identify my desired load.
Primer type, powder lot, barrel length (vs "book length"), internal friction characteristics, brass differences, plus more variables, some controllable, some not - you work with what you have.
I would find it highly unlikely (well nigh impossible) to ever see a completely linear (in Klem's terms, elastic) powder-MV graph due to all the variables plus some measuring uncertainties. I'm not a benchrest shooter nor as good a shooter as some of you guys but the physics and mechanics of the internal ballistics, coupled with all the uncertainties which are never quantified, these all militate against thinking you will find your perfect load in 10 shots.
ps one other thing going unmentioned, and this is just a theory of my own, is that premium barrels will probably show less distribution/variations than rack grade if only b/c they have a much more premium, controlled and quality-oriented production rigor. But that's just a theory of mine. Satterlee's stuff could also be making advantage of this effect as he is concentrating on prs/1000-yd matches, those guys don't use the rack grades we oft-times have.
I would venture to say that if any 10-shot string were repeated under similar, controlled circumstances at close-to-same-shotcount (for barrel internal similarities), you would see an oscillating string with different peaks/valleys from the first string you shot. Hopefully they would overlap each other... and theoretically, after several of these overlapping strings, the wide-varying MV's/powder charges and the narrow-varying MVs/powder charges (ie, "nodes") would become evident. I have yet to see anyone do this several-string test and have yet to see the graphs/data, but mechanically that's what I would expect.
"Down the floor, out the door, Go Brandon Go!!!!!"