text: Medium Capacity bombs Medium Capacity (M.C.) bombs were designed to address the shortcomings of General Purpose (G.P.) bombs, which had a charge-to-weight ratio of about 27 per cent (contemporary German bombs had a ratio of 50 per cent). M.C. bombs were to have a charge-to-weight ratio of at least 40 per cent and use explosives of greater power, although shortages often led to inferior explosive types being used. High Capacity (H.C.) bombs had a charge-to-weight ratio of up to 75 per cent. M.C. bombs had greater blast effect than G.P. bombs but had casings which were robust enough to confer a considerable capacity to penetrate.
  Grand Slam
  On 18 July 1943, after the Dams raid, the Controller of Research and Development at the Ministry of Aircraft Production (MAP) received a requirement for twelve Tallboy Small [] bombs, 60 unfilled Tallboy Medium (Tallboy) bombs and 100 Tallboy Large. Lack of capacity led to work on the Tallboy Large being stopped on 30 September. Interest in the Tallboy Large, renamed Grand Slam on 22 November 1944, after the term Tallboy appeared in the press, increased after better understanding of the effect of the Tallboy was gained by the inspection of targets in Europe. The Tallboy was discovered to be too small to destroy concrete buildings with direct hits; only near misses which opened a  under the foundations were found to be effective. In September 1944 the German V-2 rocket bombardment of London began, which had been expected by the British since Operation Hydra (the attack on the Peenemünde research centre on the night of 17/18 August 1943), and Grand Slams were considered as a weapon to be used on V-2 launch sites.