I was watching this on the History Channel and from what they were saying it wasnt destroyed but had not been completed due to the death of the scientist who was overseeing the project. Then they went on to say that after the Gulf War it was dismantled (destroyed) and they later found that he had been ordering these parts to build the gun from British who were unknowingly supplying these parts through other purchasers.
That program is where most of my information on this subject came from.