Abstract : High progressivity/density (HPD) propellants are under consideration at the Ballistic Research Laboratory (BRL) for a variety of enhanced ballistic applications. The HPD concept involves the tailoring of the mass generation rate to match the increasing chamber volume as the projectile moves down the gun tube. This can be accomplished physically by designing a grain which will increase in surface area at a designated point in the ballistic cycle. It can also be done chemically by formulating grains with compositions that vary throughout the grain. As these layers burn through, the burn rate can be tailored to change at specific points in the ballistic cycle.