Bunnings no longer have Ammonium nitrate for sale. It is a fertiliser that is hard to obtain now because of the potential terrorist problem. The Fertiliser grade was not as dangerous as the basic Ammonium Nitrate . For a long time now, make it "safe/safer" as fertiliser, the granules were treated with a surface coating. For it to be easily made explosive the nitrate is mixed with diesel fuel for easy detonation. It can and is mixed with sulphur to form gunpowder and has been for many years, back to the cannon and flintlock days. Kept "clean" it is quite safe.
Years ago there was a boat load of bulk Ammonium Nitrate blew up in a Texas port and made a big mess of the port.
From Google. "Texas City explosion of 1947, industrial disaster sparked by the fire and explosion of the SS Grandcamp on April 16–17, 1947, in Texas City, Texas. The blast set off a chain of fires as well as a 15-foot (4.5-metre) tidal wave. Between 400 and 600 people were killed, with as many as 4,000 injured."
