I've been extensively testing a particular cartridge, with a variety of bullets and a single 'baseline' powder.
I make up 20 loads, with the same bullets, but with 0.20gn increments of charge weight, and shoot them over my Magnetospeed.
I then take the chrono data, and plot MV against charge weight, to look for MV plateaus.
Each individual bullet will have a MV flat spot, somewhere in the plot.
I repeat this experiment but with a different bullet designs/weights.
The powder remains the same throughout.
I had expected that each different bullet design/weight would have an MV flat spot at different MVs and charge weights.
However when I look at all the data together, whilst the various MV flat spots all occur at different MVs, they all occur at a common charge weight.
This suggests to me, that there is a single magic charge weight for the cartridge in question. Or rather, a single magic pressure, which will always produce the lowest ES, regardless of which bullet weight/design it is pushing.
The magic charge weight in question may not yield a suitable MV for every bullet (some may simply be too slow to be useful). However that magic charge weight does consistently yield the lowest ES of all the charge weights tested. For instance, at the magic charge weight, 95gn and 140gn projectiles will all be spat out with an ES of 2-3fps – but the 95gn projectile may have an impractically slow MV.
Have any of you noticed anything similar? Is low ES exclusively a product of cartridge geometry and pressure – and completely independent of projectile design/weight characteristics?
I'd be interested to hear your thoughts.
I make up 20 loads, with the same bullets, but with 0.20gn increments of charge weight, and shoot them over my Magnetospeed.
I then take the chrono data, and plot MV against charge weight, to look for MV plateaus.
Each individual bullet will have a MV flat spot, somewhere in the plot.
I repeat this experiment but with a different bullet designs/weights.
The powder remains the same throughout.
I had expected that each different bullet design/weight would have an MV flat spot at different MVs and charge weights.
However when I look at all the data together, whilst the various MV flat spots all occur at different MVs, they all occur at a common charge weight.
This suggests to me, that there is a single magic charge weight for the cartridge in question. Or rather, a single magic pressure, which will always produce the lowest ES, regardless of which bullet weight/design it is pushing.
The magic charge weight in question may not yield a suitable MV for every bullet (some may simply be too slow to be useful). However that magic charge weight does consistently yield the lowest ES of all the charge weights tested. For instance, at the magic charge weight, 95gn and 140gn projectiles will all be spat out with an ES of 2-3fps – but the 95gn projectile may have an impractically slow MV.
Have any of you noticed anything similar? Is low ES exclusively a product of cartridge geometry and pressure – and completely independent of projectile design/weight characteristics?
I'd be interested to hear your thoughts.
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