So I had a thought... Probably not a new one, but I haven't yet come across it exactly. I'd appreciate the feedback of the more experienced/observant cast bullet shooters out there. "Papa smurf" had a related thought so I know others are thinking along the same general lines.
You would think since immediately prior to departure from the bore the base edge of a bullet is confining the gas pressure and restraining inertial wobble that a major impact to accuracy would be the beginning of blow out of this trailing edge due to gas pressure (+ other forces), and subsequent net off axis forces imparted to the bullet. Asymmetric venting during departure would impart forces, and further erosion/scarring could additionally influence the creation of net off-axis forces. Non uniform release of inertial forces could also tend to throw the shot.
Trailing edge failure could explain a lot of the correlation between bullet hardness (and gas checking) and better accuracy at higher velocities (and higher muzzle pressure). A stronger bullet trailing edge should result in smaller imperfections at departure, more uniform mechanical release, and thus less net off axis forces, and better accuracy.
It would be neat to examine bases of plain base lead bullets below and well above the velocity where accuracy had significantly degraded, if you could recover them without much impact damage and look for gas erosion/scarring/fracture of the base surface, and particularly imperfections of the base edge where it departs the muzzle.
Any thoughts, observations, references to prior discussion of same?
Anyone ever shot a uniformly soft lead bullet vs. one with just the very base quench hardened? Or how about a gas check that was just a crimped on ring (a cup with no bottom, but a perfectly flat bottom edge) extending just past the base of the lead bullet?
Best regards,
DrB