Also known as "the Elswick 110 ton gun." These were some of the largest breech loaders ever constructed, although they were of limited usefulness as their very heavy weight meant that only two guns of this size could be carried on each ship. The very heavy projectiles and large amount of powder required to fire them also meant that these guns had a slow rate of fire. In hindsight, this gun was too ambitious for a time when smaller 12 and 13.5 inch (30.5 and 34.3 cm) guns had many constructional problems.

The following description is from "British Battleships" by Parkes:

"During proof at Woolwich one of the Victoria's guns was found to have bent, and when again submitted for acceptance was put through a long series of trials which brought out other defects. It was therefore rejected and replaced by one specially strengthened, which served as a model for those in the Sans Pareil and held up her commissioning by a further sixteen months. The 110-ton gun was never tested to destruction, and although supposed to have a life of seventy-five rounds, this estimate was often questioned. It was a slow firer, never made good shooting, and proved costly to repair and reline."

The differences between the twelve guns constructed were so large that the "Mark I" designation was abandoned and they were known individually by their serial numbers. Number 1 and 2 guns were made of A tube/breech piece - the breech attached to this section - 17 hoops extending to the muzzle, 1 long hoop and 10 short hoops/8 hoops/7 hoops. All parts were made of steel forgings. The later guns were only slightly less complicated.

• ^The shrapnel shell carried 2,330 iron shot pellets of 4 oz (113 gm) each.
• ^The propellant was in eight bags.
• ^Outfit in Benbow was 37 AP, 44 Common, 11 Shrapnel.
• ^Victoria class outfit was 32 AP, 38 Common and 10 shrapnel.