Here is some information that may be helpful to noonanda’s query.
The armament onboard the union flotilla would have included guns ranging from 12lb howitzers to a 10 inch SB on the USS Cumberland. Cumberland also carried a “70lbr” rifle as aft main deck pivot and 22 x 9 inch Dahlgren SB’s in broadside. Exactly what the stated 70lbr rifle was has been debated but I would guess a Parrott of some definition. It was CSN Captain Buchanan’s concern for the ability of that gun to penetrate armor (even that of the CSS Virginia) that caused him to attack Cumberland first. FWIW, the sinking of the Cumberland was the result of damage inflicted by Virginia’s 1,500 lb iron ram, although her guns were doing deadly work as well. The boat howitzers are frequently overlooked in listings.
The USS Congress carried 4 x 8 inch SB guns and 48 x 32lbr SB’s in broadside. I am guessing that the 4 x 8 inch guns were main deck pivot mounted guns.
The USS Minnesota carried 2 x 10 inch SB’s (probably main deck pivot mounted Dahlgrens), 28 x 9 inch SB’s (undoubtedly Dahlgrens) and 2 x 8 inch guns ) probably main deck pivot mounted Dahlgrens).
USS Roanoke carried 1 x 10 inch SB (probably main deck pivot mounted Dahlgren), 28 x 9 inch SB Dahlgrens and 14 x 8 inch SB Dahlgrens. The latter two types served as the broadside armament. The USS Monitor carried 2 x 11 inch Dahlgren SB’s in a single turret.
Other ships of the Potomac flotilla are omitted here as their participation the festivities had little or no material impact on the naval affairs of Hampton Roads until after the CSS Virginia was scuttled May 11. Later that year the US Navy attempted to force the James River. Participating yankee vessels were the Galena, Port Royal, Aroostook, and Naugatuck Monitor in a rather one sided affair at Drewry’s Bluff.
24th Michigan stated that the early yankee “gunboats” were armed with 12, 32 and 42lbr SB’s along with some Parrott guns and “swivel” guns. True, but limited to western waters and mostly the City Class boats by Eads and others. Anything constructed as a turreted ironclad (single or double) would have carried the newer Dahlgrens (or perhaps Parrotts). As to the 15 inch guns the entire US military had a single prewar experimental 15 inch tube. It was dismounted and in storage at Fortress Monroe in March of 1962. Dahlgrens drawings for the 15 inch guns bearing his name were not created until April 6th (? as I recall – see my earlier articles on this subject in the Artilleryman Fall ‘07 and Winter ’12 for more details). I believe divediggers range estimate is about right for larger guns.
As for Carl's observations perhaps the following will help. The 9” Dahlgren was not accepted for US Naval use until Dahlgren protégé Catesby ap R. Jones was assigned the task of overseeing the sea trials for those guns February of 1856. That was the first instance where a navy officer was assigned duties as “Ordnance Lieutenant”. The ship? The USS Merrimack! The 11” Dahlgren was also given it’s sea trials by Jones in 1857 under the command of Dahlgren on the USS Plymouth (?). The 15 inch balls would have gone into service at the same time as the guns which were first available in September of 1862 as I recall. The projectiles weighed 440lbs as solid shot, 400lbs as cored shot and 352lbs as shell.
Interestingly, USS Merrimack (CSS Virginia), USS Minnesota and the USS Roanoke were all USS Merrimack-class 44 gun (originally 9” Dahlgrens) auxiliary steam screw frigates. Obviously deck pivot guns were added later.
The CSS Virginia mounted 2 x 7 inch single banded Tredegar made "Brooke" rifles as bow and stern pivots (designation as "Brooke" rifles respectfully debated by some), 2 x 6.4 inch single banded Tredegar made "Brooke" rifles in the #2 & #3 broadside positions, 2 x 9 inch Dahlgren "Hotshot" guns in the #4 & #5 broadside positions, the remaining 4 broadside positions were 9 inch Dahlgren SBs.
I hope this helps and please do let me know if I have erred anywhere here.
