IIRC, the sabot, at least in an M-1 Abrahms isn’t even formed until striking the target. The entire round could be considered a sabot, I guess, but the killing part comes on impact.
http://en.wikipedia.org/wiki/Sabot
I think you are referring to the plasma jet formed by the Munroe effect when a High Explosive Anti-Tank (HEAT) round strikes its target.
http://en.wikipedia.org/wiki/Shaped_charge
The sabot in an anti-tank round is a spacer that keeps the long tungsten (or, in the case of the M1, depleted uranium) penetrator centered in the shell casing during handling and initial firing. Since the penetrator is essentially a large, very hard dart, a base plate is needed to allow the expanding propellent gases to deliver their full power to the penetrator; otherwise, they would just blow past it. Once the penetrator, sabot, and base plate exit the bore of the cannon, aerodynamic forces peel the sabot and base plate away and allow the penetrator to speed to the target, usually at speeds well in excess of 4000 fps. These rounds are referred to as Armor Piercing Fin Stabilized Discarding Sabot (APFSDS) rounds.
While both deliver kinetic energy to the target, the HEAT “penetrator” is created only at the moment of impact. The penetrator in the APFSDS is manufactured component of the round.
As for the Sandia self-guided bullet, it might have useful applications in sniping, if you can get the electronics to survive the shock loads from firing and the guidance mechanism to function properly. Not an easy task, even in a much large diameter round. See, for example:
http://en.wikipedia.org/wiki/Extended_Range_Guided_Munition