BHN and Pressure
A quick internet search shows dozens of sites where success in shooting cast bullets is equated with some relationship between the hardness of a bullet (BHN) and the chamber pressure in the gun.
One relationship is that BHN * 1422 should equal pressure.
Another is that pressure should be between BHN * 480 * 3 and BHN * 480 * 4.
The word "obturation" is often mentioned.
BHN is the ratio of: force applied to a ball in contact with the test material for a given time; to the area of the semi-spherical indentation in the test material made by the ball. Units are kilograms and mm squared. Converting to pound-feet units, we find that BHN * 1422 expresses the ratio in pounds and inches squared.
Now 1422 looks like the 1422 in the first relationship above, and like the 480 * 3 in the second relationship. (480 * 3 = 1440)
The BHN testing dimple/crater/indentation area in the test material and the force applied for a given time have nothing that I can imagine to do with peak or average or initial chamber pressure.
So the contention is that for a given pressure, if BHN is too low, something bad happens, (I can't find out what), and if BHN is too high the bullet won't obturate-gas leaks by and the gun leads.
Does anyone out there have any information or data supporting this?
Is it nonsense science?
Thanks;
joe b.