Quote:
Originally Posted by glowe
There is a direct correlation between velocities and pressures - BUT . . . the only criteria for demonstrating this is to use the exact same loading techniques, bullet, primer, crimp, and brass, and as you increase the volume of the same powder, you will see a direct linear increase in pressure and velocity.
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I doubt they are linear. If the pressure doubled, I doubt the velocity would double. Because the more the pressure gets the bullet moving, the sooner it is out of the barrel and the less time that pressure is acting on it. Double pressure for the same amount of time might double the speed (though friction isn't linear either), but when the distance and not the time is fixed, they won't have a linear correlation.
That said, there is a correlation, and chronographing is all most of us can do.
But say I had a book load that claimed to be 30,000 psi and resulted in 1000 fps from my gun. If I felt my robust gun was safe with 40,000 psi loads, a linear relationship would suggest I keep loading more powder until it hits 1,333 fps. However, I tend to think this would be a bad idea and that with most powders it would result in a pressure higher than my target.