 
  
Speaking of bore obstructions, what am I likely to find in the bore of a former municipal park muzzleloading cannon?  Concrete?  Mud?  Rubbish?  Projectiles?
This is likely an insurance gun, a carronade, Congrieves Pattern from the early 1800s.  The 9-Pdr RML dated 1874 has been sold on the Detachment Matross in Gatineau.