Re: Grand Slam
Also Tallboy and Grand Slam were precision weapons, only dropped by 2 squadrons (617 and 9), and required much training to use effectively. The HC bombs were purely designed for area bombing and did not even have fins or streamlining.
Tallboys were not considered expendable; crews were under orders to bring them back if they could not drop them on the designated target (which must have made landing interesting!).
There's a lovely story in Paul Brickhill's The Dambusters. When the first Grand Slam was completed the RAF and Wallis wanted to examine the in-flight stabilisation provided by the fins. It was therefore decided to bury a high-speed film camera on the range, pointing vertically upward, in order to capture the required footage. After much debate it was decided that the safest (if also the most cynical) place to put it was in the centre of the target. Of course, 617 proceeded to release the bomb in precisely the right place, ensuring that with Wallis' superb design the bomb arrowed down, striking the target less than 10' from the centre of the aim point. Bye-bye camera...