Generally speaking, .5 or higher is considered a good ballistic coefficient, suitable for long-range shooting. However, it does depend on shooting conditions and what, precisely, you’ll be using the bullet for.  When long-range shooting, for example, you’ll want a higher ballistic coefficient so that the bullet can overcome the effects of environmental factors like wind, which have a greater effect the longer the distance the round travels. For long-range hunting, you’ll want a higher ballistic coefficient for the same reasons and to ensure a clean, ethical kill.  It also depends on the particular round you’re shooting. Long-range rounds like 6.5 Creedmoor will have a higher ballistic coefficient.  Remember, however, that a high ballistic coefficient often comes at the cost of other factors that affect ballistic performance, like bullet weight. Be sure to weigh these factors against ballistic coefficient to make sure that you’re choosing the right bullet for your needs.