Early hooped trunnion guns that differed in some construction details and some external dimensions but were of similar performance. Used by both the Army and Navy. Like most early British breech loaders, these guns were too weakly constructed and were later chase hooped. This lengthy process caused such long delays in construction that they never made it onto a warship. Instead, two of them were used on gunnery school boats and a few more were employed in coastal defenses.

It had been intended for the ironclads Sultan and Hercules to each mount eight Mark I guns, but this was cancelled in 1885. It was also planned to rearm the ironclad Rupert and the cruisers Imperieus and Warspite, but this was cancelled in 1884. Next, it was planned to rearm the armored ram Belleisle with four guns in 1886, but by 1888 these guns had still not been chase hooped and repaired so this was also cancelled. Finally, there was an attempt to speed delivery of the cruisers Galatea and Aurora, which were awaiting 9.2"/31 (23.4 cm) Mark V guns, but the performance of the Mark I was considered completely inadequate for this role. It should be understood that the Royal Gun Factory at Woolwich had great difficulty in meeting the Navy's needs during the 1880s. As a result, the completion of many ships was delayed during this period.

The Mark I was originally 26 calibers long while the Mark II was originally 28.4 calibers long. After chase hooping, both guns were then 25.57 calibers long.

Following chase hooping, the Mark I consisted of 'A' tube taking the breech piece, a 141" (358 cm) liner secured by screwed ring/breech piece (this was made from coiled wrought iron), '1 B' and '2 B' coils, four hoops to the muzzle, 'D' coil (wrought iron) with trunnions, 'C' coil (wrought iron). All parts were steel unless notes. A bronze balance sheeth and steel elevating band were shrunk over the breech end. The 'D' and 'C' coils were replaced in the naval guns by steel hoops and then designated as Mark IA. The breech block was of the interrupted screw type using a hand worked three-motion mechanism, but in some Army guns there was no hinged carrier. In these guns, the block was completely withdrawn from the gun by handles. These were given the prefix 'UC' while those Army guns with the three-motion breech had the prefix 'C'. These latter guns had the '2 B' and part of the 'C' coil replaced by steel hoops.

The Mark II differed from the Mark I in having the trunnions 2.65" (6.7 cm) closer to the muzzle and in having the 'C' and 'D' hoops replaced by steel hoops and then being designated as Mark IIA.

Altogether 17 Mark I guns were made of which 11 were for the Navy, but four of these were later transferred to the Army. Two Mark II guns were manufactured.

Data from:

• "British Naval Guns 1880-1945 No 6" article by John Campbell in "Warship Volume VI"

05 August 2006

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