text: The  nose sections were filled by upending them to pour in  of Torpex explosive a bucketful at a time. Once the tail section was connected, the Grand Slam was  long,  at its widest diameter and weighed . As with the Tallboy, the fins of the Grand Slam were angled and generated a stabilising spin and the Grand Slam had a charge-to-weight ratio of 43 per cent. Four fuzes were provided, one specially made for the Grand Slam with an 11-second delay, the No. 53 with a thirty-minute delay, a No. 53A with an hour's delay and a No. 37 which had a delay of 6 to 144 hours. The first bomb arrived at Woodhall Spa on 20 January and fifteen were expected by the beginning of February.
  Lancaster B.Mk 1 (Special)
  The ten remaining Dambuster Lancasters were sent for storage at the end of 1944 and 617 Squadron was increased from two flights to three, at the expense of 51 Squadron, a Halifax squadron of 4 Group, which lost a flight. To carry the Grand Slam, specially modified Lancasters were necessary but these would have to be subtracted from the production of ordinary Lancasters, when several 5 Group squadrons were also converting to Lancasters from the Halifax. The weight of the Grand Slam meant that only new aircraft would be able to carry it, rather than converting existing and worn aircraft; 32 B.Mk 1 (Special)s were ordered from Avro. There was little agreement on what equipment the specials should carry and Avro backslid on production to keep the new Avro Lincoln, a Lancaster derivative, on schedule. Work began on the specials at the end of January 1945 and two had been built by 13 February, twelve were due within ten days, 24 by month's end and the remainder in March.