Just to confirm Tripler, C-4 and other plastique compositions require both high thermal impulse and an intense pyroshock in order to explode. I don’t think any mechanical shock, such as impact from a bullet or being dropped from any height will result in even partial detonation. They are also not sensitive to moderate electrical shocks; you would have to hit a brick of C-4 or Semtex with an extremely high voltage impulse with enough amperage to vaporize part of the material in order to initiate detonation. Fire by itself will not initiate these explosives, though if they combust under pressure it is possible to get a detonation wave started.
Pure RDX in crystalline form, however, is fearsomely sensitive, and has to be handled with special precautions. Nitroglycerine (which is no longer used in modern dynamite) is not especially sensitive at lower temperatures but can become extremely sensitive if it develops impurities, and has the nasty habit of leaching into other substances and then being initiated due to high local stresses (like the Hertzian stress of a ball bearing in contact with a bearing race) and so has to be handled very carefully to prevent any kind of spillage.
TATP, HMTD, and other “home-brew” explosives have a tendency to be extremely sensitive (hence, why commercial manufacturers don’t produce them), exacerbated by the often impure chemical sources used to manufacture them. Such substances are best disposed in place whenever possible because it is not possible to assess sensitivity.
Stranger