Developed from the M47 "General Patton" tank, the M48 was the mainstay of the US Army and Marines in Vietnam.
The Blackhorse arrived in Vietnam equipped with the new M48A3, powered by a diesel unit, having replaced the earlier M48A2 ( which featured a gasoline engine and was very prone to fire) prior to their departure for RVN.
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 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 battlefield 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 M48 had been designed for combat in Europe against Soviet tanks. The M48A3 had, for 1968, a state-of-the-art fire control system. In 1968 computers were mechanical. . Range to the target was provided 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 merged. As the distance between the mirrors is exactly 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 in Europe 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 peacetime qualification, it was possible to stop from a speed of 20 mph, acquire the target, and get off a first round kill at 2,000 yards in seven seconds. This precision fire control system was almost irrelevant in Vietnam where typical engagement ranges could be measured more reasonably in feet than in yards. So in D company it was common to take the gunner out of the turret and put him on the back deck with an M16 or M79 for close-in protection. This also afforded him some protection from mines, and indeed the TC and loader often rode on the turret roof or the hatch lips when mines were expected. The TC laid the main gun by eye, and fired using the commander's override control or a lanyard to the manual trigger on the main gun. Most M48's in Vietnam had the commander's .50 cal. mounted on top of the cupola on a simple pintle mount. This location gave a better field of fire, was faster to reload, and less prone to jamming than when the M2 was placed on its side inside the armored cupola. But the TC was terribly exposed to fire when firing the M2.
Rocket Propelled Grenades were a constant threat, and D company tanks countered this threat by mounting Pierced Steel Plank, chain link fence, and spare track blocks on the fenders to prematurely detonate incoming RPG's. The bustle rack was extended with welded steel, and the turret sides buttressed with extra .50 cal. ammo, C-ration cases, and the crew's duffel bags. The cases of C-rations strapped to the infantry rail on the turret, like the PSP and track blocks, 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 dissipated the force of the explosion away from the armor. 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.
Canister and HE were the primary main gun ammunition types used. Beehive was effective, but usually in short supply. WP was useful, but dangerous to carry since it ignited if split open by a mine or RPG strike, so crews tended to expend it as soon as possible. HEAT briefly was popular after NVA tanks were engaged at Bien Het, but HE was usually preferred against bunkers. Above the main gun was 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.
Crew: 4 (driver, gunner, loader and TC)
Total = 52 tons
Armor (Homogeneous cast steel)
Taken from David Avery's 'D' Troop 1/11th ACR Web Site which is highly recommended.
Jim Fitzpatrick, D Coy, 1st Sqdn, 11th ACR.
Armor of the Vietnam War; (1) Allied Forces, Michael Green & Peter Sarson, Concord Publications Ltd