US forces in Korea used five
basic types of hand grenades, many of which can
easily be converted to rifle grenades.
1. Offensive grenades (pic,
upper left). Contain an explosive charge
filler of flaked TNT in a body with sheet metal
ends and pressed fiber sides. Designed for
demolition effect and to stun the enemy in
enclosed places.
An older model Mark I is shown
above, but went to the Mark IIIA-1, about 14
ounces, for Korea. The earlier dangerous impact
type fuse was replaced with a time fuse as with
the fragmentation grenade. By 1953, our
concussion grenades were simple half-pound
blocks of C-3, an explosive resembling opaque
yellow plastic, packed in cardboard, and into
which was screwed the standard fragmentation
timed fuze. The fragmentation grenade was much
more widely used in defensive situations. The
Chinese and North Koreans frequently used
concussion grenades as their primary grenades
for assaults, as they pose less danger to
attacking troops. However our soldiers would
sometimes be stunned but still recover in time
to continue fighting effectively.
2. Fragmentation grenades
(pic, upper middle). Contain an explosive
charge in a metal body, designed to break into
fragments upon the charge exploding. They have
a killing radius of 5 to 10 yards, and
fragments are dangerous up to 50 yards.
Normally thrown less than 35 yards, that means
'duck' until they explode, and the time
delay after pulling the safety pin was from 4.0
- 4.8 seconds.
The MarkIIA1, fitted with the
M10A3 fuse, was most commonly used. Weighing
about 21 ounces, constructed of cast iron with
serrations, this grenade produced about 1000
potentially lethal fragments.
3. Chemical grenades
(pic, bottom row and middle right). Designed to
produce a toxic or irritating effect, a
casualty effect, a screening or signal smoke,
an incendiary action, or some combination. Some
of these grenades, as with the TH M14 thermite
(bottom center, and enlarged bottom left
without fuze), come with metal straps which
prevent rolling, and an M200A1 igniting fuse
with only about 2 seconds of delay after safety
lever release. Baseball-type tear gas grenades
(bottom right) are special issue for riot
control, using a CN filler.
The most common chemical
grenade was the M15 White Phosphorous. Weighing
about 31 ounces, using the M6A3 fuse with a 4.0
- 4.8 second time delay, the M15 had a burst
radius of about 25 yards and burned for 50 to
60 seconds. Officially intended as screening,
casualty and harassment, the WP could illum a
suspect area for the gunners while still giving
any enemy in the area other things to worry
about. The Mk1 (middle right) was an
Illuminating grenade.
4. Practice grenades.
Contain a reduced charge for safe use in
training.
5. Training grenades
(upper right). Containing no explosive charge
or chemical, these are for grenade throwing
practice.
6. Bangalore Torpedo. As
did Communist
forces, we sometimes also used the bangalore
torpedo. This is just a 3 foot or so length of
pipe, filled with flaked TNT or plastic like
C-3, and capped at both ends. The fuze is
screwed into one end of the pipe. It is
primarily intended to blow paths through
obstacles like barbed wire, and so is normally
inserted under them, with the blast effect
blowing the obstacle material up and to the
sides.

Chinese Bangalore Torpedo
Grenades come in different
sizes and shapes, for different purposes, but
all have two things in common. First, they are
hollow so they can be filled with the explosive
or chemical filler. Second, they contain a
threaded hole into which a fuze can be screwed
or inserted.
A grenade is essentially a
small bomb, but works very much like a simple
firecracker. A firecracker is made up of a
paper body filled with gunpowder and has a
small fuze. When you light the fuse, it burns
down to the powder and blows the paper body
apart. A grenade works exactly the same way,
the main essential difference being that the
grenade's fuze is lighted by a mechanical
device rather than a match.
The below image shows a
cross-section of the grenade and fuze parts for
a fragmentation grenade. The basic action is as
follows:

1. Holding the grenade in
the throwing hand, thumb over the safety
lever, pull the safety pin (A cotter pin,
bent at one end, ring attached to the
other, pull force of 10-35 pounds. In
immediate threat situations, the ring
could be pulled enough to straighten the
cotter pin, and then flipped out
easily).
2. When the grenade is
thrown (safety lever released), a spring
throws off the safety lever and rotates
the striker into the primer.
3. The primer contains
material like the head of a match. When
struck by the striker, it ignites and
sets fire to the fuze, or powder train.
The fuze burns at a controlled rate,
providing a time delay (usu 4-5 seconds).
When the flame of the fuze reaches the
detonator or igniter, it causes action on
the filler.
4. A detonator is similar
to a small blasting cap. Very sensitive
to heat, when the fuze burns into it, it
causes the grenade to explode.
5. An igniter is a cap
that burns rapidly. It basically sets
fire to the filler causing a rapidly
expanding gas which bursts the
container.
6. The MarkII
fragmentation grenade shown uses a
detonator.
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Model 36 Mills Bomb |
Note by Arthur Snell,
dsnell@mpx.com.au
Australian veteran of later Maylasian
campaign:
'We (Aussies &
Brits) were still using the WW1 designed
Grenade No 36M or Mills Bomb. It weighed
about 1lb 11ozs or 2lb. Used a 4 or 7
second fuse. The 7 second fuse was
normally used when the Mills Bomb was
fired out of the rifle mounted grenade
cup launcher. It was a defensive pattern
grenade and shrapnel could kill up to 80
yards. Therefore it was thrown from
behind cover or thrower immediately laid
down after throwing. In bunker or strong
point clearing it was definitely
overkill, but still the best I have ever
used. The outercasing was cast iron and
in pattern to assist fragmentation. It
worked on split pin and curved lever
similar to your Mk IIA1. '
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