Sorry for my analytical inclinations here, but here I go....

My somewhat superficial reading on antiproton reactions says that each annihilation will yield several pions that travel at most 21 meters (though vacuum) before decaying into gamma rays. The inevitable gamma rays will have energies upwards of 60-80 MeV. These gamma rays will travel ~100 meters through air and lose half their energy. On the other hand they will deposit the same amount of energy in a 1 cm-thick iron casing.

So I'm looking at an explosives scenario here:

~16.282 micrograms of antiprotons contains roughly 1.0068E(+19) antiprotons, and has the same potential reaction energy as 1 tonne of TNT

~A 2-cm diameter sphere of iron has a mass of 33 grams. If the annihilation reaction occurs at its geometric center this spherical mass will absorb half the energy contained in 1-tonne of TNT, roughly 2 billion Joules.

~ Since gamma rays travel at the speed of light they would deposit their energy everywhere throughout the bomb casing virtually instantaneously. Sufficive to say, the entire casing would be instantly vaporized, and a 135 million-degree Celsius shockwave, consisting of ionized iron nuclei, would expand outwards at an average speed of over 348 km/sec (unless some teraflops supercomputer techie would care to dispute me).

~ So I think the explosives potential here is enormous. Thermite reactions are used in solid rocket booster btw so the similarity IMO would be in the form of a "big bang".