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CGN-38, and CG-47 classes of ships carry the
Mk 45.
5"/38
The 5"/38 semiautomatic DP gun was the
mainstay of the U.S. Navy from 1939 until the late
1960s. Single or twin mounts made up the
secondary batteries on early cruisers and
battleships. One or two single mounts are now the
main battery of the older DDs, FFs, and guided-
missile frigates (FFGs). The twin mounts are the
secondary gun battery on battleships (BBs). For
short periods, an efficient gun crew can get off 15
rounds per minute for single mounts and 30
rounds per minute for single twin mounts. The
projectile weighs 55 pounds and has an effective
range of 18,000 yards.
3"/50
The dual-purpose, semiautomatic 3"/50
gun was planned during World War II. The
enemy’s use of combat suicide planes and dive
bombers prompted the need for rapid-fire
weapons having a larger explosive projectile
than 40-mm guns. Although the 3"/50 gun was
not produced in time for wartime service, it
proved to be a very effective gun. Becoming
standard throughout much of the fleet, it
replaced the 40-mm twin and quadruple
mounts on all combat ships. Most of the
mounts installed were open twin mounts;
however, a few single mounts were installed.
The 3"/50 fires 45 rounds per minute per
barrel and has a range of 14,200 yards. A few
of these mounts remain on major combatant
ships, but most are found on auxiliary and
amphibious landing ships.
76-MM/62
The Mk 75 76-mm/62-caliber, rapid-fire,
dual-purpose gun mount was developed in the
late 1960s to combat increased aircraft target
speeds and the cruise missile threat. Because
of its light weight, it is suitable for
installation on the new guided-missile frigates
and missile hydrofoil boats. It is a water-
cooled single mount with a rate of fire of 85
rounds per minute and a maximum range of
17,800 yards. The gunhouse, which is not
manned, requires only three handlers to
reload the magazine.
CLOSE-IN WEAPON SYSTEM (CIWS)
The close-in weapon system (CIWS) was
developed to provide the fleet with a close-range,
hard defense against antiship cruise missiles,
fixed-wing aircraft, and surface targets. The
system is an automatic, fast-reaction, computer-
controlled radar with a rapid-fire 20-millimeter
gun. It combines a single-mount fire control
radar and a six-barrel Gatling gun that fires
depleted-uranium projectiles at a rate of 3,000
rounds per minute. Its projectiles are 2.5 times
heavier than those made of steel. The system
has a high-kill probability. This system is
suitable for installation on most ships as a single
unit. It permits smaller ships to have a degree of
self-protection never before possible. (See fig.
20-2.)
GUN FIRE CONTROL EQUIPMENT
Gun fire control equipment must solve a
difficult problem. It must direct the guns to hit
Figure 20-2.—Close-in weapon system (CIWS).
20-3
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