Americans didn't drop the bomb...

[Dr Jekyll]

Yertis said:

I'm assuming that Lancaster is to a different scale?

Yes, the Victory was supposed to be about 95ft long with 170ft wingspan, 48 tons total weight. The Lancaster was about 70ft and 100ft and 25 tons.

For comparison the B29 was 99ft long, 142ft wingspan and about 55 tons.

[GliderRider]

CanAm said:

And in the first test of the Grand Slam bomb, dropped from 16,000ft., it attained the designed speed of just over 700mph.
Barnes Wallis was well aware of the performance of British bombers at the time (see Wellington), and proposed a new 6 engined design to reach the required 40,000 of his original earthquake bomb.

There was also the Disney Bomb, or rather bombs, which were rocket propelled to accelerate them downwards faster than gravity alone would. Disney Bomb

The free fall Tallboy had a an impact speed of 750mph, whereas the comparable Disney Bomb could reach 990mph.

[ssc100]

It has been said that the Lancaster was the only aircraft capable of carrying the A bomb without being heavily modified unlike the B29 that needed to be very heavily modified to carry the bomb, the RAF offered the Americans the use of lancasters and had even perfected air to air refuelling for the mission, but in the end politics reared its ugly head and some American general ruled that it must be carried out by and American aircraft with American pilots. But it may have ended up slightly different at the end , look it up, that info is out there to read .