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The Mark I was an Elswick design used only in coastal batteries and was not interchangeable with the other Marks. The other Marks were Woolwich designs which were used afloat but were mainly utilized for coastal defense batteries world-wide. These other Marks were interchangeable with each other and the ships that carried them eventually had a complement of different Marks. Mark I consisted of a "complete liner"/A tube/breech piece, three "B tubes to the muzzle/C hoop, trunnion piece and jacket. Mark II used a liner, "alpha tube"/A tube/breech piece, two B tubes not to muzzle/C hoop, trunnion piece and jacket/D hoop. Mark III was A tube/breech piece, two B tubes to muzzle/C hoop and tube/two hoops and trunnion piece/hoop and screwed breech ring. Mark IV was A tube/breech piece, B hoop and tube to the muzzle/three C hoops/D hoop, trunnion piece, screwed breech ring and jacket. All used a cylindrical interrupted screw breech block with a hand worked 3-motion mechanism, although HMS Renown was reported to have a continuous motion mechanism in 1897. For the Mark I, II and III, the breech screwed into the breech piece and for the Mark IV it screwed into a breech bush which was screwed into the end of the C hoop. A few modified designs were also built. Mark IIA were guns with separate bore and chamber liners. Mark IIIA was two guns different from the Mark III in having the one of the B tubes replaced by two hoops and having shoulders on the A tube over the chamber for greater longitudinal strength. For all Marks, an "A" in front of the Mark meant that the gun was fitted with a continuous motion breech mechanism, used on coastal defense barbette mounting, and the Mark I* though Mark IV* meant loading tray stops and locks for the same mounting. Altogether, ten Mark I, five Mark II, fifty-two Mark III and nine Mark IV guns were manufactured. Nomenclature note: The 10" (25.4 cm) Mark V was a proposed gun that was never built. Originally, this was to be a 40-caliber gun similar to Elswick Patterns P, Q and R used on ships built for foreign navies. However, in 1901 it was learned that the USN was planning armored cruisers armed with 10" (25.4 cm) guns and so a new 50-caliber gun was planned. The coast artillery branch was also interested in this design, as the early versions of the 9.2" Mark X had proved unsatisfactory. Design was a wired gun with inner A, A and B tubes with a jacket. The design for this gun was sealed, but it appears that none were ever ordered. |
After 10-in (25.4 cm) guns on HMS Renown
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