Mons Meg:
https://simple.wikipedia.org/wiki/Mons_Meg
Another Photo broadside, and of the section that failed, retiring the weapon (It's just a flesh wound). Looks like a hoop failure. Apparently range was around 2 miles, balls have been found that far away from it's firing point. note the holes for tools used in re-assembling the screwed parts. Probably a slightly bigger set like the coupling tool also below.