Re: 338 solids vs. leadcore
If I had to guess and that's really what I'm doing you have it backwards, or chance found you week spots in the steel. It looks at thought there is a hole cut in the middle of your target, if it was done with a torch it would have compromised the brinel strength around the hole, making is softer than the surrounding steel.
The reference to the RPG, is similar to a APFSDS or EFP (explosively formed projectile). In concept I know what you are referencing but lead it to soft for such a task. Its melting point is to low, so it would lack the required density. In a round like you are referencing you would nee a metal like tungsten, or depleted uranium. Copper is used in gorilla warfare to make an EFP which is a liquid under pressure the essentially cuts through steel. Very scary cheep and effective weapon!