Why would they destroy all of it? Maybe the homemade bombs, but the ammo could just be turned over to the Iraqi army for their use? 50 cal is about $1 a pop, if were talking BMG. Instead we'll destroy THIS ammo, and buy them some new ammo? Someone just wanted to see something go boom, I think!
Lessons learned LOOOOOOONG ago, that mucking around in the enemy's ammo dump can be unhealthy....
They are frequently booby trapped to prevent THEIR ammo from becoming YOUR ammo....
What little may be of common useage -- is probably not worth the risk --- in a time of "plenty"..
Semper Fi