A series of low powered weapons
originally designed as boat and landing guns. Mark 4 was a Bethlehem
Steel design with a side-swing carrier breech block. Mark 7 was Erhardt-type
landing gun built by the American-British Manufacturing Company with a
horizontally-sliding breech block. The Mark 9 was a monobloc Bridgman
"wet" gun designed for submarines and used a vertically-sliding breech
block. This mark was used in a special retractable mount, as can
be seen in the photographs below. Mark 9 Mod 0 was a built-up gun
while Mod 1 was a monobloc design. Mark 11 a similar design used
as a landing gun and built by Bethlehem with a vertically-sliding breech
block. Mark 13 was a boat gun built by Driggs with a semi-automatic
horizontally-sliding breech block. The Mark 14 was a boat gun adapted
by the Poole Engineering and Machine Company during World War I as an AA
gun for destroyers. Mark 14 Mod 1 was used aboard patrol craft and
had a muzzle blast reducer and a breech counterweight.
Landing guns were mounted on mobile
carriages, each gun being provided with a limber for the transport of ammunition.
Some guns were given AA mountings during World War I and then used on flush-deck
destroyers. Many guns remained in service on these destroyers until
the middle of World War II.
About 80 guns were supplied to Britain
during World War II, mainly on Lend-Lease ships.
All guns fired fixed ammunition and
had similar ballistics, but were of differing construction, the early guns
being of the built-up type while the latter were of monobloc construction.
The built-up guns consisted of a multi-tube, forged-steel barrel, with
one hydraulic recoil cylinder located above the barrel, and one hydropneumatic
counter-recoil cylinder located beneath the barrel.
