Drilling the ordinary bullet down to the same weight as a .22 but retaining the same diameter of the bullet is bad for several reasons:
Same friction in the barrel as the original bullet(while good sabots have less friction).
Higher retardation, due to lower weight compared to the diameter of the bullet, so velocity will drop more sharply.
Unless you get the drilling perfect, you will unbalance the bullet, risking it tumbling in the air. Not good for ballistic purposes, since both accuracy and velocity will decrease sharply.
Due to those factors, energy will most likely be lower than for the .22 sabot.