Two dams were attacked with Tallboys in 1944, The Sorpe by 9 Sqn in October, 4 direct hits including one dead center of the road at the middle of the crest. Didn't even come close to breaking it (Tallboy had a much smaller charge than Upkeep) and the Urft Dam in the December where both 617 and 9 Sqn attacked the dam (though most of the aircraft didn't bomb due to bad weather). One direct hit on the crest which took out a large chunk, but well above the water line, so no breech. Tallboy and Grandslam were not designed to penetrate large amounts of concrete and in almost all occasions where the bomb did hit a hardened target, it exploded within the concrete before entering the space under the protection causing limited damage to the area directly under the point of the detonation (If the bomb didn't break up first or only partly detonate, which happen on more than a few occasions). Most of the major structural damage was done by near misses undermining the structure attacked, which is exactly what Barnes Wallis had designed the weapon to do.
V3 would have been a game changer had it actually worked!!! The weapon had two major problems, firstly the secondary charges along the barrel had a tendency to pre-detonate before the shell past them (thus retarding the shell instead of accelerating it) and secondly due to the smooth bore nature of the barrel, the shell (which was fin stabilized) didn't spin and tended to topple in flight. The longest range they got in trials was around 60NM, which was a shorter range than Paris gun of 1918. Most of the damage to the V3 site was done by a Tallboy going down one of the gun shafts, exploding and exposing an underground water course which then flooded the lower levels and drowned a lot of Germans and forced labour who were sheltering down there.
Last edited by MAINJAFAD; 1st Jun 2014 at 13:20.