Thread: RANGE CHECKS
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Old 08-31-2020, 12:40 AM
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Check out "The Perverse Nature of Standard Deviation":
https://www.shootingsoftware.com/ftp...%20of%20SD.pdf
Variance means very little on it's own.
5-6 shot variance or even SD means little.
Also a particular SD only applies to that load.
SD of 10 in one load has a different meaning than SD 10 for a load with a different average velocity.

What the target looks like is what you want to maximize.
I have collected a lot of data and targets and good targets and good SD correlate only some of the time.
You know what they say about statistics (lies, damn lies, ...).
The predictive powers only become apparent with large data bases not groups of 5 or 6.

Most revolver loads are only partially full of powder.
I believe this to be one of the major sources of velocity variance.
But after years of playing with some fillers, I decided it was not worth the effort as little improvement was noted
and while some targets were impressive it was not a universal effect.

"Mic" McPherson has suggested pushing the bullets further down in the case to mitigate this problem but I have never had the time to pursue this much.
This also goes against what some riflemen do when setting the bullets to (just) touch the rifling to center the bullet and eliminate freebore or bullet jump.
It's an interesting idea from an expert however.
Metallic Cartridge Handloading: Pursuit of the Perfect Cartridge by M.L. McPherson

Collecting chronograph data is a worthwhile venture, but I use it mostly to try and calculate the actual pressures involved and keep out of trouble.
Feeding this data back into QuickLOAD makes it more accurate.
Also a totally horrible SD (like 10+ times worse than expected) may indicate a problem in ignition or just a bad recipe.
For instance I have given up on using 1680 in the .445 because a combination of poor targets and a lot of blowback
(poor cartridge seal) is also attended with variance in the 100's fps and SD in the dozens.

Variance and SD are not completely worthless but are given much more value than they deserve especially when it comes to revolvers IMHO.
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Last edited by Nemo288; 08-31-2020 at 12:44 AM.
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