Int14200 Col2520
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Colossus has two turrets, each carrying two 12 inch rifled breech loading guns of 45 tons. This section shows how the guns are arranged within the turret, and gives an overview of the loading process.

Each turret rests on a ring of rollers. The turret base rides on these rollers, which are tapered to ensure the turret remain central.


The beams that carry the guns are connected in a frame with the recoil cylinder in between. The frame is pivoted at the front, so that the guns can be elevated and depressed with the smallest cutout in the turret frontal armour. Hydraulic elevation rams are fitted to the centre of the turret base and these elevate the frames.

The hydraulic systems in Colossus uses plain water as the hydraulic medium.


The guns are 12 inch Mk IV of 45 tons, with a length of 25 calibres. The gun barrels are connected to a slide by two straps, thus dispensing with several hundred years of gun manufacturing tradition – no trunnions. This arrangement means that the guns can be mounted close together.[2] The slides connect to a piston that moves within the recoil cylinder.

Loading equipment is now shown. External to the turret are the two rams that will be elevated into line with the guns when elevated to the reload position of 13 degrees. The internal reloading frame and saddles are mounted at the rear of the turret.

The guns, therefore can only be reloaded when they are trained to line up with the loading rams. 90 degrees on the beam for the starboard turret, and 85 degrees for the port turret.


Here we see the port guns in their reloading position, trained to Red 85 degrees The guns are fully run in (retracted) and are elevated to 13 degrees.

The external loading rams are raised. In the sister ship to Colossus, HMS Edinburgh, loading rams are fixed in the raised position.

The armour plating base of the turret is now shown. Two access holes are cut in the armour at the rear of the turret. Although not shown, it is possible that there would be hatches to close these holes when not actually loading.

The armoured turret base also carries gearing that connects to gear wheels driven by two hydraulic turning engines situated in the bunker space below. It is probable that the turret could be trained through 360 degrees in about one minute.

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