What was the average failure rate of aerial bombs in the Second World War, and whose were better – the USAAF, RAF, Luftwaffe, Russian VVS, Regia Aeronautica, or maybe Japan’s IJAAS?

I’m wondering because I came across an interesting statistic in Ian McLachian’s book of Eighth Air Force Bomber Stories (See Amazon below) He notes that German records showed that of 672 bombs dropped by B-24 Liberators of the USAAF on a raid near Dortmund on 2nd nov 1944, 152 failed to explode. As McLachian points out, presumably some of those were delayed-action, but all the same that’s an astonishing 23% failure rate!

Perhaps it’s not all that surprising.

Even now, three-quarters of a century later we are still regularly finding unexploded bombs around Europe, especially in the UK and Germany. Only a few weeks ago flight operations at London City Airport had to be suspended for almost two days while they removed a 500kg bomb discovered in the dock next to the runway.

Since 2010, the UK military has dealt with 450 German WW2 bombs – almost 60 per year!

Matt Brosnan, a historian with the Imperial War Museum, estimated that around 10% of bombs dropped on London during the Blitz, failed to detonate. So, were German bombs better than American bombs?

I wonder how bomber crews felt about it. They wouldn’t have had access to any post-action intelligence reports on bomb failure, but they must have noticed the discrepancy between bombs leaving the aircraft and detonations on the ground. Most of the bombs they risked their lives to deliver, exploded. Was a 90%-75% detonation rate considered OK? It certainly wouldn’t be in some other branches of the military.

Failure rates were a huge issue for submariners, Axis & Allied, which you can understand. They might spend maybe hours maneuvering carefully into an attacking position while risking counter-attack, only to experience the agony and fury when their torpedoes failed to explode. The Type VII U-boat, for example, went to sea with only 11 torpedoes. Every one of them was critical because unreliable weapons drained confidence and morale, as the US Navy submariners could testify; their Mk14 torpedo was notoriously unreliable.

So, the question is: what was the average failure rate for aerial bombs in WW2 and whose were best? Do you know?