Both turrets seem fairly similar in outwards appearance; both are cylindrical iron constructions, containing one or two guns. The difference between the two systems came in how they were supported and rotated. The Ericsson turret sat on the upper deck, standing eight-nine feet clear of the deck. It rotated around a central spindle which pivoted in the hold; this supported the weight of the turret in action. The Coles turret pierced through the upper deck, resting instead on the lower deck. It therefore had a lower profile, standing only four feet clear of the deck. The edges of the turret sat on a roller path on the lower deck, letting the turret as a whole rotate.

These two systems had different advantages and disadvantages. For the Ericsson system, the spindle imposed two main constraints on the turret. Firstly, the spindle was in the centre of the turret. This meant that any penetration through to the lower decks had to be off centre, and therefore could not be accessed throughout the full range of the turret's rotation. This limited the crew's ability to access the turret, and to pass ammunition - typically, the crew of an Ericsson turret had to rotate it to the centreline to pass new ammunition into the turret, slowing the already glacial pace of reloading for muzzle-loading guns. This was not a problem for the Coles turret. As this was supported at the edges, the turret centre was always available for shells to be passed through. The spindle was also not in constant operation. When the ship was not in action, the turret stayed in contact with the deck. Prior to going into action, the spindle and turret had to be jacked up by about an inch to allow the turret to rotate. This imposed a delay, which could by a problem if a ship was surprised. The gap created by the raising of the turret also meant that enemy shells could jam the turret if they impacted its base. The base of the Coles turret was protected, and the turret needed little preparation for action. The Coles turret, meanwhile, required more precise engineering than the Ericsson. As the turret passed through the upper deck, and did not sit on it, it also created paths for water to leak into the ship. These leak paths could be blocked with canvas for long passages, but it still remained a problem in action.