 The Davidka's propellant chamber fires inside the mortar tube (barrel) as does a conventional mortar, but the 3 inch (76.2 mm) caliber of the barrel is much smaller than the caliber of the warhead of the bomb.It is therefore an oversized conventional mortar, where most of the bomb, and especially its center of gravity, remain outside the barrel—an aerodynamically unstable design, which only worked at all because the center of pressure was still within the barrel.The head of the bomb was essentially a large can filled with nails, rocks, or any other material which could be used for shrapnel.