A close analogy to a rubble pile is a shot and wax slug projectile commonly fired from a shotgun as opposed to a monolithic pure lead slug, with the former having a lower density as it is loosely held together by wax and is composed of numerous individual lead bird shot spheres.
Dinosaur Pile-Up | Barney Rubble | Bamm-Bamm Rubble | William A. Pile | pile | General Sir Frederick Pile's | Frederick Alfred Pile | Chicago Pile-1 | Betty Rubble | A Great Big Pile of Leaves |