The United States Sentencing Commission seems to be changing the punishments to include the "actual" weight of the controlled substance.

Take for example oxycodone. Effective November 1, 2003 they will use the actual amount of oxycodone in a particular pill.

Amendment for Nov 1st

Also, the punishments seem to be the same for possession, possession with intent, distribution, manufacturing, or conspiracy --- it is all based off of weight.