Last week I had the opportunity to to attend the shooting of a reconstructed medieval bombard of the fellow reenactment society Albrechts Bössor from Sweden at Middelaldercentret Nyköbing in Denmark. Especially the 1.000 g Load was the loudest bang I heard in my life so far - despite wearing ear protectors. The bombard weights about 300 kg and was reconstructed after an original from the city of Cologne.
Bombard with 500 g powder load
https://youtu.be/G8fvueTCaOE
And the same with a 1000 g powder load
https://youtu.be/mdkmpPWpT68