The AI version:
Generally, a Full Metal Jacket (FMJ), copper-jacketed bullet from Western Cartridge does not fragment when striking a human skull. Instead, it is designed to remain structurally intact and punch cleanly through the dense bone. In forensic ballistics, the behavior of these rounds on impact typically breaks down as follows:
Minimal Deformation: FMJ rounds feature a lead core entirely encased in a harder copper or copper-alloy jacket. This design prevents the bullet from expanding or breaking apart, allowing it to easily pierce both the entrance and exit plates of the skull.
Bone Comminution: While the bullet itself usually remains one piece, the extreme transfer of energy shatters the human skull bone upon entry. This causes the skull to break into sharp, irregular bone fragments (comminuted fractures), which can travel as secondary projectiles into the brain cavity.
Exceptions for Fragmentation: Fragmentation is rare but can occur if the bullet is fired at extreme velocities (e.g., high-powered rifle rounds) or if the bullet is destabilized and tumbling (yawing) before impact, which stresses the copper jacket and causes it to break apart.
---30---
The M-C carbine (aka short rifle) and Western Cartridge ammo used by LHO or other assassin was on the cusp of being a high-powered round, ~2000 fps. i gather such a slug would not be expected to fragment.
Evidently, one relatively undamaged WC slug was presented to the WC as evidence, although it was not recovered from Gov. JBC's body, but rather (possibly) a hallway inside Parkland. The chain of evidence on the CE-399 is dubious.
Other fragments from slugs were found in the limo.
A curiosity: A slug or fragment struck a curb near James Tague, with enough force to splinter concrete or other matter and cause a cut in Tague's face. But that is a puzzler. Could a fragment do that? Tague was a quite a distance from the limo. Seems iffy.
I have reasonable doubts about the LNT-SBT. Seems squishy.