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We used the M-48A3 Main Battle Tank as our primary weapon. This fully tracked vehicle, with a combat weight of 52 tons, mounted a 90mm gun-cannon, a co-axially mounted 7.62mm M-73 machine gun, and a cupola-mounted M2HB (the HB stood for Heavy Barrel, but was modified to mean Heavy Bastard) caliber .50 (12.7mm) machine gun. The tank contained two M3A1 caliber .45 sub-machine guns (aka grease guns) for individual use. Each crewman carried an M-1911A1 caliber .45 semi-automatic pistol, designed by John M. Browning. I carried an M-16A1 rifle instead of the pistol because I was paranoid about having to defend myself with only that pea-shooter against hoardes of dope-crazed North Vietnamese (hey, that's what Westermorland called them) armed with Kalasnikov AK-47 assault rifles.
We carried five types of ammunition for the 90mm gun: HEAT (High Explosive Anti-Tank) for use against armor and other hardened targets; HEP (High Explosive Plastic) for use against soft (unarmored) vehicles and troops; Canister, a big shotgun shell really, for use against troops at close range; Flechette, or "Beehive" rounds, for use against troops at close range (The round got its name from the buzzing sound the thousands of tiny darts, or flechetts made as they flew through the air); and White Phosphorous, or "Willie Pete". The Willie Pete was a dangerous round to have around. Its primary purpose was to mark targets since it made copious amounts of smoke. But because the phosphorous burned at about 2,000 degrees Fahrenheit, and because it would burn under water, it caused serious burns. Our normal procedure was to fire these things at a hillside as soon as possible in order to get them out of the fighting compartment.
The vehicle was capable of a top speed of 40 mph on a road. It weighed 52 tons with a full load of main gun and automatic weapon ammo. It was powered by a Continental AVDS-1790 engine, mated to an Alison CD-850 transmission. Known collectively as a power-pak, the unit weighed 6 tons. AVDS stood for Air-cooled, V-block, Diesel, Supercharged (although it was actually Turbo-charged). The 1790 indicated the the engine displaced 1,790 cubic inches (my Corvette has 350 cubic inches for comparison). The vehicle averaged about one gallon per mile, although traversing broken terrain brought the average down to about 2 gallons per mile.
The armor on the M-48A3 was made from homogeneous cast steel, and varied in thickness from 11 inches at the front slope, to less than two inches at the floor of the hull. The armor on the turret was about four inches. The turret, with gun, weighed approximately 18 tons.
The vehicle was separated into three compartments: the driver's compartment, the fighting compartment (where the Gunner, Loader, and Tank Commander fought), and the engine compartment. The armored cover on the engine compartment, which we referred to as the back-deck, weighed 2 tons, so engine swaps were not as fast as Roger Penske's.
The entire purpose of the tank is to carry the main gun into battle. The armor is provided to ensure that the crew is protected from shrapnel (the main cause of battle-field casualties) and small arms fire. The crew exists solely to serve the main gun. The driver gets the vehicle to firing position, the TC selects targets, the loader ensures the weapon is loaded with the correct ammunition for the target selected, and the gunner makes sure the round strikes the target in the area of maximum vulnerability.
The M48A3 had, for 1968, a state-of-the-art fire control system. Let's examine what state-of-the-art was in 1968.
Range to the target was provide by a stereoscopic range finder, which functioned similarly to a 35mm camera. An end-box on each side of the turret exterior held a prism-type mirror. Turning a hand-crank on the range finder would pivot these mirrors until the double-image in the range finder's eyepiece came together. Since the base length between end-boxes was known precisely, and the angle each was turned to was known, a little trigonometry provided the range (in meters) to the target. This information was displayed on a range indicator, and also fed to the ballistic computer by a rotating shaft.
The ballistic computer was a collection of gears and cams--nothing was solid-state--which had a handle so that the gunner could select the type of ammunition that was to be fired. Each round had a different muzzle velocity, and therefore the computer had a different cam for each type. The computer would take the range data, merge it with the velocity data, and via a set of rotating shafts, supply this information to the gun's super-elevation mechanism, resulting in the gun being elevated above the gunners line of sight sufficiently for the round to overcome the downward pull of gravity on its way to the target. The gunner's sight however remained locked onto the target.
A good crew was able to put the first round on target 90% of the time, but this required excellent teamwork and communication on the part of the entire crew. In peace-time qualification, it was possible to stop from a speed of 20 mph, acquire the target, and get off a first round kill in seven seconds. In the fog of war however, it usually took considerably longer.
I have included a photo of my M48-A3 on strongpoint duty on Hwy 19..
The cases of C-rations seen strapped to the infantry rail on the turret acted as a stand-off shield. If an enemy anti-tank rocket struck the C-rations, it would explode prematurely. Since anti-tank rounds require a certain stand-off distance to function effectively, the C-rations effectively increased that distance to the point where the round was rendered ineffective. It was also the only place we could store the rations, since space in the vehicle was at a premium and occupied mostly by ammunition.
Above the main gun is a 1 million candle-power Xenon searchlight. This light had both a white light and an infrared mode. It was boresighted with the main gun and gunsights so that it could be used to illuminate a target at night.
Mounted on top of the searchlight was an E8, a 35mm 16-tube disposable CS gas canister launcher. We hated this thing because it was very unpredictable. It would sometimes fire itself, usually at an inopportune moment. It was also vulnerable to enemy fire, which could also set it off and give the crew a big dose of CS gas (we had protective masks, but they were usually stowed in the bustle-rack and not reachable).
The tracks were composed of 64 track shoes, and each track (there were two) weighed 2 tons and lasted for about five hundred miles. The tracks were considered to be weapons.
These candy bars came in the Sundry Packs we were issued at infrequent intervals. They were designed to withstand the tropical heat of Vietnam, which normally caused most chocolate bars to become liquid. Whatever it took to prevent them from melting also made them taste terrible. So rather than eat them, we gave them away to the kids that lined the roads when we drove through a village. The Montegnards loved the things.
They were also good crowd-control devices. Since they were harder than depleted uranium, we would throw them at unruly crowds of ARVNs who got too close to the tank.
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