I think Ill go with Sketch (ChristCAF) on this one.
First because he is a squadmate and one of my best friends
Second because he working with Bombs, Explosives and the like every day. He is highly trained in this area and his information is pretty solid. Sorry, no offense, But watching a DVD on it isnt probably as good a source.
Im sure gun fire *could* make one go off in the right situation, but I think this would be pretty rare. So modeling part of the DM based on a rare case doesnt make sence.
Besides Bombers are fragil enough and easy to kill to a skilled pilot in the right plane.