Was this the Daisy-Cutter used in Viet Nam? I thought the bomb they used there fell by parachute and had a long probe that allowed for an airburst when the probe made contact with the ground.
The one that I saw used in 1971, Central Highlands, VN, was as you described. I was on a very small FSB, near Charlie Ridge, called "Linda" or hill 270. There was an abandoned FSB on hill 327, several Klics away, which still had old culvert halves and other miscellaneous stuff that was left behind. It was used as an OP, due to height and location, by the NVA. I often called in fire missions, both day and night unexpectedly, to drop 10-15 rounds (105 or 155 mm) on hill 327 as surprises for Charlie. The Army decided to drop a blockbuster and remove all easy hiding places on 327. I was basically an FO on hill 270 and was told to observe from the 30' tower, where I worked while on duty. Everyone on 270 was ordered to stay inside their bunker/one-man hootch or wear flak vest and steel pots, if outside, at the appointed hour/minute. Using 20x, large field of view, binocs that were part of the I.O.S. instrument, I watched as the blockbuster was dragged out of a high altitude cargo plane by a parachute, and dropped at a high rate of descent, even with the small chute. There was a 10-20 foot pole on the bomb nose, for above ground detonation. Even though we were far enough away, the same relative altitude of the blast as our hill made the shockwave a minor danger but a major bone rattling, deep penetrating, thud. I can only imagine the effects of the same shockwave, at a closer range. Needless to say, the top of hill 327 looked nice and clean, like freshly plowed dirt, after the blast.
BTW .. that was the same hill 327 that the Marine sniper, Gunny Carlos Hathcock, used as a home base for a while, in the late 60s.