Metal wise or shape wise?
I know they mentioned using blunt shapes to measure variances in trajectories, they have plans to go to a more recognizable projectile shape. As to materials I don't think they said, but due to the use of magnetic fields, the projectile should be made of conductive materials like copper and silver...I am guessing they are exploring elements and perhaps are putting less expensive heavy metals in the interior and wrapping it in conductive material, so perhaps the thing is like a super-supersonic HP!
