The heavy siege cannon or conversely a fortification or coastal artillery piece was by its very nature larger and more powerful than their smaller field piece cousins.
These pieces where too heavy for field armies. Some of the largest weighted up to 100,000 pounds and fired cannon balls weighing up to 800 pounds.
Effective range for most coastal artillery pieces of the early to mid-19th century was around three miles. Which explains one of the reasons why that number was the boundry of a countries territorial waters until the 20th century.
Typical ammunition included solid shot, explosive shell, grapeshot and hot shot.
Hot shot involved heating the cannon ball in a furnace and firing the super heated shot into the highly flammable innards of the wooden sailing ships of the day.
The recoil of the piece was taken by the rails the heavy artillery piece rested upon.
This metal piece is in 25mm scale and was from a now defunct manufacture in Texas. I painted it in the 1980's for 19th century Colonial Battles. The gun platform is a scratch built piece and is part of a larger trench, field siege set I also built for Colonial Battles.
And the real thing, a 32 pdr that protected the harbour of Halifax from a potential 19th century invasion fleet.