Blue Dot is one of those powders that I just don't trust. I've played with it a bit and I've had some unpredictable results like dramatic pressure swings and unpredictable velocities. I would use a filler in the case to hold the powder closer to the primer to prevent powder detonation in stead of burn.
You could try using Trail Boss. That would get your velocities in the 1500 fps range though so it may not work for what you're going for.