Why do I want an SG of 1.5 or higher?

You want an SG of 1.5 or higher because you want to make sure you are maximizing the BC of the bullet. Bullets can fly accurately, group precisely, and appear to be perfectly stabilized when flying with a SG below 1.5, but can have measurably depressed BC’s. Another reason you want to aim for an SG of 1.5 or higher is to have that extra 0.5 of SG as a safety margin. If you aim for an SG of 1.0 and conditions are less than optimal, you have a problem.