The M42 and KB-1 are very similar dual purpose submunitions in the category of DPICM (Dual purpose Improved Conventional Munition). The KB-1 was made in Yugoslavia,and is similar to the M42 made in the USA. The dual purposes are anti-armour and anti-personnel.
The outer sleeve of the munition is its anti-personnel fragmentation (a matrix of ball bearings set into plastic in the KB1). The interior has a small amount of high explosive above an armour-piercing shaped charge. Despite its short length (80mm), the end opposite the ribbon is empty and provides the "standoff" that allows the shaped charge to form and achieve its armour-piercing properties.
Arrow A points to the firing pin that may be unscrewed (it is not in this example).
Arrow B points to the blocking bar, which is in place and blocking the firing pin in this picture
The ribbon used may be any colour, but is usually white, black or green. It unfurls when the submunition is released and orientates the device so that it falls with its shaped charge facing downward. The ribbon loop vibrates as it passes through the air. It is attached to a threaded firing pin at the back of the munition. The firing pin cannot move forward into the stab-sensitive detonator because its forward movement is blocked by a bar with a recess into which the pin fits. As it falls, the vibrating ribbon unscrews the firing pin. When the firing pin has unscrewed several turns, the front of the pin disengages from the recess in the blocking bar and a spring moves the blocking bar to one side. The firing pin is now free to move forward into the detonator. The firing pin does not have a spring. When the device lands in an upright position, inertia carries the firing pin into the detonator and initiates the device.
If the device does not fall far enough to unscrew the firing pin, it will not be fully armed on arrival.
If there is any obstruction on the thread of the firing pin, the device may not be armed on arrival.
If the device does not land in the correct orientation or strikes obstructions such as buildings or trees, it can fail to initiate. Its ribbon may catch on obstructions and so hold the firing pin away from the detonator.
Moving or handling an unarmed device can rock the ribbon from side to side and allow it to arm.
Moving or handling an armed device can make the firing pin slide forward into the stab-sensitive detonator.
If the ribbon end of a munition is clearly visible, it is possible to see whether the blocking bar has slid entirely to one side, meaning that the device is fully armed.
If the thread on the firing pin attached to the ribbon is clearly visible, it may be possible to estimate how close to fully armed a device is. The M42 and KB-1 will kill. If there is any uncertainty about its state, a munition should always be destroyed where it is.
The KB-1 contains:
High Explosive charge: 30-33 g of TNT/RDX
Anti-armour shaped charge liner
Fragmentation matrix jacket KB1; cast steel fragmentation jacket M77
A simple fuze mechanism designed to detonate on impact.
As with all fragmentation munitions, only one person should approach this device at a time.