Accuracy nodes during load development


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bds
July 9, 2014, 01:35 AM
For me, accuracy is everything.

Many reloaders may ponder the aspects of OAL/COL, seating depth, neck tension, chamber pressure build, chrono'd velocities for the lowest SD number, etc. but in my opinion, accuracy on target is the final word on reloading variables that results from consistency.

I used to hold on to the notion that accuracy improved as I worked towards near max powder charge from the supposition that higher chamber pressures translated to more consistent powder burn to produce more consistent muzzle velocities. This has been the case for me with most powders but during the current component shortage, I had a chance to do load development for different powders where I observed accuracy that modulated.

An example would be a work up of powder X from 4.5 gr to 5.5 gr for a specific bullet. Accuracy could be observed with 4.6 gr load but decrease with 4.8 gr load. Then accuracy improve with 5.0 gr load but decrease with 5.2 - 5.4 gr. When I initially experienced this doing various 9mm/40S&W/45ACP load developments, I chalked it up to shooter error/fatigue but when I more or less got similar results on subsequent range trips, I began to wonder.

Could this be the demonstration of accuracy nodes and have you experienced this with your load development? '

And if so, could .2 - .3 gr change powder burn characteristics enough to affect accuracy measurable on the target?

Is this the reason why with some powders, we could get lighter target load near the start charge that are accurate but also get loads that are accurate at higher powder charges?

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ArchAngelCD
July 9, 2014, 01:39 AM
Over the years I have found very similar outcomes.

Usually you will find 2 "sweet spots" in a powder load range. One is usually down near the bottom and the other in the upper end but usually short of the max.

murf
July 9, 2014, 01:47 AM
i agree with archangelcd. most all powders will have a node in the lower third of the load range and one in the upper third of the range.

my 270 load (130 gn berger) runs 2750fps out the muzzle. shoots bug holes.

murf

gamestalker
July 9, 2014, 02:01 AM
Ya, I know what you mean. I to have had do some new work ups the result of powder shortages and have taken notice of similar accuracy nodes, especially with high powered rifle. But I chalked it up to not having needed to work with other powders until this present shortage we've all been dealing with. Kind of
neat though, in that I now have a larger log of great loads to fall back on, that if not for this supply and demand problem, I likely never would have known.

GS

Walkalong
July 9, 2014, 04:04 PM
Accuracy could be observed with 4.6 gr load but decrease with 4.8 gr load. Then accuracy improve with 5.0 gr load but decrease with 5.2 - 5.4 gr. ....................................................

Could this be the demonstration of accuracy nodes and have you experiencedYes, although it isn't always that simple.

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