This is a 20mm Bombard from Zvezda. I left off the small crew and added 28mm crew from some Hundred Years War artillery from Black Tree Design.
The bombard was the original big gun. They were laid out on the ground because they didn't have a carriage that could handle the beast.
These were wall breakers, but also prestige items. Henry the VIII had twelve of them cast for his war in France, the Twelve Apostles. Due to their high cost they were often heavily decorated.
The model itself is nice enough, though the canon has some unfortunate casting errors; which, come to think of it, is fairly accurate from an historical perspective.
The BTD figures are nice. Simple, easy to paint. Good clean casts as is normal for their stuff.
Looking at this I realize that I failed to cover a couple of the holes for the tabs on the 20mm figures. The timber bracing behind the gun is my favorite part of this model. It really looks the part.
The barrel is removable in case I want to do a wagon for it at some point.
The 28mm crew look just fine on this. Since there was not really a standard size for these guns this could easily be a smaller example of the breed.