It was recently reported that 350 tons (US) of explosives went missing
in Iraq. These "extremely powerful, conventional explosives" consist
of HMX, RMX and PETN, type material. If one assumes that there is
approximately 116.67 tons of each material, what would be the total
potential explosive force (in kilo-tons, mega-tons or in Hiroshima
bombs) that could be created by detonating all the material at once?

Bonus question with 2X tip multiplier (up to $20 additional): If the
materials differ much in explosive potential, what would be the
maximum explosive potential, and minimal explosive potential?

Example: If HMX is twice as explosive as RMC or PETN, and the
stockpile consisted of 99% HMX how much force could be produced.
Likewise if HMX were only half as explosive and the stockpile
consisted of 99% lesser explosive material, how big of a boom?

I would like as accurate an answer as possible, given the amount I?m
offering to pay.

I think HMX is the most powerful of the three, and at
http://www.vectorsite.net/ttpyro1.html it says that it has about 75%
more explosive yield than TNT.  So if it was all HMX, that would be a
little over 0.6 kilotons, or about 1/30 of a hiroshima bomb.

The relative ?strength? of explosives can be extimated using the
Berthelot approximation, which assumes that the relative ?explosive
strength? of a material depends on the product of the change in
internal chemical energy due to the explosion and the volume of gas
produced by the explosive reaction.   See
http://www.fas.org/man/dod-101/navy/docs/es310/chemstry/chemstry.htm.

Using this approximation, the relative strengths of PETN, HMX, and RDX
(not RMX) are:

  PETN = 1.78 x TNT
  RDX =  1.74 x TNT
  HMX = 1.73 x TNT

(The explosive combustion of 1 kg of TNT releases 2.715 x 10^6 J of energy.)

If there were equal amounts of each material, then the TNT equivalent would be: 

    350 * (1.78/3 + 1.74/3 + 1.73/3) = 612 tons TNT

The range of explosive potential would be between 1.73*350 < x < 1.78*350 
(606 tons < x < 623 tons).  Not a big range, and probably well within
the error of the Berthelot Approximation.

The best estimate of the explosive yield of the Hiroshima device is
15,000 tons TNT equivalent (+/- 20%). (See
http://www.physicstoday.org/pt/vol-56/iss-2/p14a.html) so 612
tons/15000 tons = 4.1% of a Hiroshima event.

I was in Afghanistan when 60+ tons of explosives and ordinance (1/6
the stuff lost from Iraq) was detonated about 12 km from my tent. I
have no idea what the megaton equivalent was, nor do I care. But it
was a BIG boom; the shock wave caused the tent sides to billow
suddenly. The mushroom cloud lasted for the better part of an hour.
The sight made for great memento photographs. Just thought I'd share
my personal experience.