In many ways, the Rheinmetall-Borsig MK 108 30mm cannon was considered
to be a masterpiece of weapons engineering, due to it's compact size, ease
of manufacture and hitting power. Although it was first designed by Rheinmetall-Borsig
in 1940 as a private venture, the design was finalized in 1942. It met
a later RLM requirement for a new aircraft cannon that could knock down
enemy bombers with the lowest expenditure of ammunition and stay beyond
the range of enemy defensive fire.
In short, the
MK 108 was a blow-back operated, rear-seared, belt fed 30 mm cannon using
electric ignition and was charged and triggered by simple compressed air.
One drawback was that once installed, there was no method to adjust the
gun's harmonization. One distinctive physical feature was the very short
gun barrel, which gave the MK 108 a low muzzle velocity of 500-540 meters
(1640-1770 feet) per second. The maximum rate of fire was 650 rounds per
minute. The operating sequence for the MK 108 went like this:
combining
a very thin shell casing with the maximum load of explosive. Tests carried
out at Rechlin (where most of the Luftwaffe aircraft and weapons tests
were done) showed that with a "M-Shell" with 85 grains of explosive, five
hits could destroy a B-17 or B-24 bomber. The second type of shell, the
incendiary, was meant to be targeted at the fuel tanks of the enemy plane.
Since some penetrating force was still needed to overcome the armor or
airframe of the target, and not have the shell break up or explode upon
contact, a hydrodynamic fuse was fitted so that the shell only exploded
once it came into contact with liquid.
to
the low muzzle velocity) and that the ammunition belts sometimes ripped
when the guns were fired while the aircraft was banking sharply, the MK
108 was chosen to be fitted in a wide variety of Luftwaffe aircraft (please
see table below) before the war's end. It was also planned to be used
in many of the project aircraft also (please see table
below), for the reasons given above: ease of manufacture, compact size
and weight and destructive power. The MK 108 30mm cannon earned a fearsome
reputation among Allied bomber crews, who named it the "pneumatic hammer"
due to its distinctive firing sound.
| Designation | Maunfacturer | Caliber | Length | Weight | Rounds/
Minute |
Muzzle
Velocity |
Projectile
Weight |
Cartridge
Weight |
| MK 108 | Rheinmetall-Borsig | 30 mm
1.18" |
1057 mm
3' 5.6" |
58 kg
127.9 lbs |
660* | 500-540 m
1640-1770' |
330 g
0.73 lbs |
480 g
1.05 lbs |
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Please
click here for a large format drawing of the Rheinmetall-Borsig MK 108
30mm cannon
(opens in a new browser window)
The Rheinmetall-Borsig
Side and Top views
|————————— 1057 mm (3' 5.6") ———————–|
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Although not a high quality photo, the small size of the MK 108 is
apparent (note hands on left)
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