What I am looking for is the Naval 150 pdr mounted on a wooden pivot slide carriage.
The description "150 pdr" and "200 pdr" refers to the weight of the projectile. For the navy, the 200 pound projectile was shortened due to limited storage space on ships. The 150 pdr and 200 pdr are the same 8 inch Parrott rifles. Only the length and weight of the projectile is different.
The Parrott rifles were prone to exploding if fired too fast. On the second assault on Ft Fisher, the Susquehanna´s foward Parrott rifle exploded after rapidly firing 88 rounds, killing four sailors and causing minor damage to the ship itself. The breech band cracked and the upper part of the breech was blown off. A total of 215 rounds from those guns were fired into Ft Fisher from the Susquehanna. The ship was also damaged just from the concussion of these guns. At the end of the war, they were removed and replaced with even larger XI Dahlgrens. (11 inch). Some Ironclads carried up to 15 inch Dahlgrens.
Here is a picture from one of the 15o parrotts barrels I have already made for my ship. The officer is scale to the gun. (I hope) :laugh1: