The band got the idea to use cannons in this song when they were rehearsing in Paris. The wedding of Prince Charles and Lady Diana was on a nearby TV, and cannons could be heard to celebrate the festivities. At AC/DC's concerts, two cannons set up behind the band were used to perform the song.
This wasn't the first time they augmented their show with nontraditional instruments: In 1980, they used an enormous bell on stage to ring in "Hell's Bells
AC/DC also wasn't the first band to use artillery on stage. When Emerson, Lake & Palmer played the Isle of Wight festival in 1970, the fired two cannons at the end of their performance of "Pictures At An Exhibition
Bertrand - Paris, France