evolution, certain conditions must exist prior to firing.
Making sure that the gun is pointed in a safe direction,
that all the loading equipment is in the fire position (out
of the way of recoiling parts), and that the breechblock
is all the way closed are just a few of the obvious things
that must be correct before firing. A typical electronic
firing circuit includes inputs that monitor these and
many other conditions, allowing firing voltage to pass
only after all safety conditions have been satisfied.
A firing cutout mechanism interrupts firing when
the gun is pointed at or near the ship's permanent
structure. A firing cutout is a mechanical device that
monitors gun position.
The components we have just described are
common to all guns. We will now discuss the individual
gun systems in the fleet today, paying particular
attention to the loading system in each one.
LEARNING OBJECTIVES: List and explain
the different gun mounts used aboard ship.
Explain crew position and responsibilities and
loading sequence when operating gun mounts.
As you read this section and study the illustrations,
note the different configurations of machinery designed
to accomplish the same task from one gun to the next.
When we are speaking of gun equipment, all directional
nomenclature (left, right, front, back) is relative to the
muzzle of the gun (the end of the barrel from which the
projectile exits when fired); the muzzle is to the front as
you stand inside the gunhouse.
5"/54 MK 42 GUN
In the 1950s as potential targets became faster and
more sophisticated, a gun with more range and a faster
rate of fire was needed. The 5"/54 Mk 42 was developed
to effectively engage these targets as well as shore
targets. Several versions of the Mk 42 gun have seen
service since then. In the fleet today, you will find only
the Mod 9 and the Mod 10; all others have been retired.
The two versions are identical in many respects. The
differences will be pointed out at the end of this section.
The 5"/54 Mk 42 is an automatic, dual-purpose gun
mount. It can be controlled either remotely from a fire
control system, usually the Mk 68 GFCS, or locally
from the mount at the One Man Control (OMC) station.
The normal mode of operation is the remote mode. The
mount fires an average 70-pound projectile up to 26,000
yards with a 48,000-foot ceiling. The gun, with its
automatic loading system, has a rate of fire of 34 rounds
As you will see, the loading system is actually two
almost separate systems, left and right. The ammunition
carrier and the hydraulic power drive units are the only
components shared by both sides. The advantage of
having separate systems is readily apparent. In the event
of a casualty, you can isolate the affected side and
continue to fire at 17 rounds per minute from the other
We will now describe the major components of the
mount as we walk through a loading cycle.
Figure 6-15 illustrates the major components of the
5"/54 Mk 42 gun. The gun is operated by the mount
captain from the EP2 panel. Electrical power is supplied
to the gun through the EP1 panel. Both the EP1 and EP2
panels are located in the compartment directly under the
mount, along with the lower hoist power drive,
ammunition carrier, and upper hoists. This compartment
is commonly called the carrier room. Inside the gun
mount, there are two manned positions: the gun captain
and the OMC operator. The gun captain has the
responsibility of monitoring the operation of the gun and
relaying bore reports (whether or not the gun bore is
clear) after each round or salvo is fired. The OMC
operator functions as a check sight observer during
normal firing. As check sight observer, he uses the
telescopic sight to ensure that the gun is trained on the
intended target. He then reports CHECK SIGHT ON
TARGET. The loader drums, located in the projectile
magazine, are served by the magazine crew. The
magazine crew is made up of Seamen from various
divisions of the ship. You may be assigned to this station.
Here, you will remove propelling charges and
projectiles from their storage bins and load them into the
loader drums at the command of the mount captain.
Some individuals from the magazine crew also serve as
members of the hot gun clearing team. The
responsibilities of this team will be described later in
When a remote order is received, the mount captain
gives control of gun train, elevation, and firing circuit
to the fire control system. When ordered to fire, the
mount captain initiates the loading cycle by pressing
the RAM ONCE or the RAM CONTINUOUS button
on the EP2 panel. RAM ONCE allows one round to be
loaded and fired. RAM CONTINUOUS allows the gun
to continue firing until it is empty or ordered to stop by