Wireman Duties

Cpl Herchkorn was assigned to Battery "B", 1st Battalion, 11th Marines
a 105mm howitzer battery (six guns, 128 men) as a wireman.
I'm not sure, but I think the Military Occupational Specialty
(MOS) code for wireman was 1811, but don't quote me. When he
left the battery early in 1966, he was still a wireman. When
he was sent back to Phu Bai for training he was a buck
Sergeant (really an Army term used to designate the lowest of
the Sergeants - they go from E-5 to E-9).
Although you have him listed as an 0811 - Artillery Cannoner
I really doubt that he had sufficient time to have gained
competence and qualification in that field. Another clue would be that no battery
would give up its qualified E-5 0811's.
There were only 6 0811 E-5's in a battery and each commanded a gun and its crew.

These guys were like gold if they were good
because it was a fairly skilled job and it required leadership ability.
A lot depended on those guys as their skill meant to
difference between the shells landing on the enemy or the friendlies.
In an artillery battery there are two means of communicating
over distance (greater than shouting range). When on the move
the only method is the use of radio. Radiomen had a different
MOS than wiremen although they both worked under the Comm
(Communications) Chief. Of the two, the radiomen were
considered the more 'elite' group.
They had to lug a heavy radio around but they were normally in the company
of officers (every officer in the battery had at
least one radio operator (the 105mm battery had a Captain as
commander, and lieutenants for Executive Officer (the senior
lieutenant), Fire Direction Officer, the Artillery Liaison
Officer and three or four Forward Observers. The FO job was
the one Herchkorn was training for when he was killed.
The wiremen, on the other hand, provided the other means of
communicating which was only available when the battery was in position.
The first thing that would happen on taking a
position was to 'string' wire.
This meant that a man from each gun would attach one end of a
spool of telephone wire to a field telephone at the gun
position and then pull the spool to the Executive Officer's
location to tie the other end of the wire to a junction box.
At the same time, a man from the Fire Direction Center would do the same.
The Exec's driver would attach the Exec's field phone to the
junction box and the battery had internal communication over
telephone line. None of these men were wiremen. The wiremen
were responsible for laying wire to more distant locations,
such as Artillery Battalion headquarters and the supported
Infantry Battalion's headquarters.
With wire in place, there was a communications network which
didn't need radios and which was not as subject to intercetion or jamming.
Unfortunately, wire was strung on the ground and
things like trucks, tanks, and people got tangled in it and broke the wires.
This is where the wiremen earned their keep. They had to
locate and fix breaks and shorts in the lines and keep the
network going. Later, when the battery moved, the wiremen had
to pick up the wire they had laid so we would have it in the next position.
The wireman's job was tough (especially when it rained which
caused lots of shorts) and thankless. Generally when a wireman had contact
with an officer it was because the 'land line'
(wire) was out and the officer was 'upset'. I can understand
why Herchkorn would want to change MOS.