I know its going to depend dramatically by what class of ship we're talking about. But just trying to figure out, when I read about naval cover for Mac on the Peninsula or Grant at Pittsburgh's landing, is there a way to think about the equivalence in land battery power? Are naval guns as effective as a land battery when not firing at ships? What percentage of a ship's guns are effectively useless because they're facing the wrong direction and can't be physically brought to bear?
One situation that comes to mind was Breckinridge's attack on Baton Rouge in August 1862. The Confederate Expeditionary Force had basically beaten the Federal garrison and had driven them back to the river to the protection of the Federal Fleet. The CSS Arkansas was intended to arrive to destroy or drive away the Federal gunboats and allow the ground forces to take the town. Of course, she broke down and was fired by her own crew to prevent her capture, so that scenario never happened. The Confederates were wary of attacking into the teeth of the gunboats now protecting the Federal soldiers and so withdrew. This is the fleet of the Federals at Baton Rouge:
Warships:
Cayuga (Unarmored screw gunboat, Unadilla class; one 11-inch smoothbore, four 24-pounder smoothbores, one rifled 20-pounder)
Essex (Converted armored gunboat; one 10-inch smoothbore, three 9-inch smoothbores, two rifled 50-pounders, one 32-pounder smoothbore, one 12-pounder boat howitzer)
Katahdin (Unarmored screw gunboat, Unadilla class; one 11-inch smoothbore, two 24-pounder smoothbores, one rifled 20-pounder)
Kineo (see
Katahdin)
Sumter (Converted river ram, formerly
CSS General Sumter, captured at Memphis, June 1862; one 32-pounder smoothbore [?])
Just for grins, this is what the CSS Arkansas would have brought to bear against them had she arrived:
CSS Arkansas (Ironclad ram; two 8-inch smoothbores, two 9-inch smoothbores, two 6-inch rifles, four rifled 32-pounders. I shouldn't leave out her ram which was reported to be: "16-foot long by 10-foot wide 18,000-pound cast iron ramming “beak,” securely bolted along eight feet of her prow timbers."