"Jeroen Wenting" wrote in
:

a concrete block three feet long used as a bomb substitute would weigh no
more than maybe 50 pounds.
Doesn't make a deep crater when falling from an aircraft at a lowlevel
penetration mission.

A 50 pound mass travelling 100+ mph should make a hole deeper than just a
foot. A 14 pound bowling ball from the 6th story of a beachfront hotel went
deeper than that many moons ago.

Dave in San Diego