The 3.5in rocket launcher M20 is
a two-piece, smooth bore weapon of the open tube
type, and is fired electrically. A bipod and rear
support permit firing in a prone position, and
the rocket may also be fired from sitting,
kneeling and standing positions. The
high-explosive anti-tank (HEAT) rockets are
capable of penetrating heavy armour at angles of
impact up to 30 degrees. Sighting on target is by
means of a reflecting site mounted on the
launcher. In firing, the front and rear barrel
assemblies are joined to form the firing tube.
While carrying, the barrels are unjoined, and
fastened together side-by-side with a carrying
sling, to be less cumbersome. A magneto-type
firing device in the trigger grip provide the
current for igniting the rockets.
The primary functions of a rocket
launcher are to ignite the rocket propellant and
give it initial direction in flight. Reactive
forces are slight since the propulsion of the
rocket is due to the jet action of the propellant
powder in the motor body, and not a gas pressure
built up inside the tube. Therefore, the tube
needs to be only heavy enough for handling in
combat, and to prevent excessive heating at
normal rates of fire.
When the propellent is ignited,
gases and flames are blown from the breech. The
area directly at the rear must be clear of
personnel or inflammable material. Because of the
rear blast, the gunner must take special
precautions to avoid injury when firing from the
prone position.
As with the heavier German tanks,
the 2.36" bazooka was not sufficiently
effective against the rugged T34, arguably the
best tank developed in WWII. Actually, it should
never have been deployed in Korea, as the M9A1
and other 2.36" models had been withdrawn
from service shortly after WWII, and nominally
replaced with the M20, of similar design but with
a larger rocket. The M20 was deadly against the
T34.
Beginning with Vietnam the Army switched to
light antitank weapons, or LAWs, such as the M72,
a one-shot, disposable weapon that weighed 5
pounds fully loaded yet could launch its rocket
with reasonable accuracy out to 350 yards.
Both the 2.36" and the
3.5" bazookas were deadly effective against
dug-in troops, and as a short-range anti-pillbox
and anti-personnel weapon, as well as against
transport and tanks.
When prepared for shipment, at
the factory the weapon was protected by fungus
resistant coats over electrical contacts, grease
films, and grease packing in the hand operated
generator which ignites the propellant. On issue,
grease-removing solvents were provided, to be
used in readying the weapon for actual
firing.
This wasn't always understood
by troops in combat, especially allies unfamiliar
with our approach. When Aussies were issued the
3.5 at the Battle of the Broken Bridge,
October '50, they fought off a large group of
NK supported by T34 tanks, but had problems
igniting the propellants. When they found out
about the grease --- later --- the problem
ceased. Funny in retrospect, but not to a guy
looking down the barrel of an 85mm cannon. Little
things can make a big difference, in chaos.