I would say real. Hard to say just which ship. I was on the Big Mo and have seen and felt a broadside. One can actually see the projectile as it travels to target. The blast and heat wave is impressive. A full broadside all nine rifles (they are called Naval rifles) will move the ship about 16 feet sideways. What is really funny is to see all of the none exsisting dust from the compartment you just cleaned appear every where after one of these lights off.. LOL
The rifling by the way is quite fast many lands and grooves actually rather shallow. Big brass rings on the projectile to grip the rifling. One can fire them from the turret, a butt handle and trigger from a 45 1911AI one at each barrel.