George,

The Laird rams would indeed have had several advantages over the Passaic class, chief among them being large caliber rifled ordnance and speed (10 knots vs. 7.) However, I question their ability to isolate any single monitor, except for possibly during transfers from one station to another. Typically, the USN monitors were in teams.

The lower profile monitors presented a smaller target, had thicker armour and a shallower draft (11.5' vs. 17') As a result, a monitor's normal course of action against such deep draft vessels would be to head for the shallows should it experience trouble or deem itself outgunned. The 15" Dahlgrens should have been able to cause some serious trouble for the Laird rams and the firing solution would be easy enough because of the relatively high profile of the target, plus heavy roundshot.

With ships like the New Ironsides, the Canonicus class, Roanoke, and the Monadnock (later), the Laird rams would have had their hands full facing quite a few 15" Dahlgren's as well as a few heavy rifled cannons capable of penetrating the rams' armor. Nevertheless, it would have been a HUGE shift in the balance of naval power, potentially allowing the CSA movement from one of its ports to another, and exposing the USN's coastal fleet to an external threat. The big advantage I see is in harrassment and using these CSN vessels to foil any US naval operations against major ports. Mobile couldn't be taken if such vessels could steam into the bay and sink Farragut's fleet. The problem the USN had is that it posessed no vessels capable of pursuing and confronting them on the high seas. This would have given the CSN vessels the initiative. Ironically, the biggest danger to the CSA would be in attempting to use the vessels in direct decisive action. By entering into combat in coastal waters the Laird rams would be exposed to all sorts of potential disasters, and playing on terms more favorable to the monitor fleet.

Henry mentioned breech loaders for the Lairds, but from what I've gathered they were to be armed with 9" muzzle loaders because the breech loaders of that caliber were very problematic. In all likelihood their individual piece load time would have been similar to that of the monitors, although of course they had two turrets.