Of all the weapons used by the warring parties in World War II,
a special place is occupied by a gun from Swiss company Oerlikon.
This autocannon was operated by the militaries
on both sides of the frontline,
but only the Allies managed to reveal its full potential.
Using this Swiss-designed weapon,
the Allied navies provided their ships with highly effective air defense.
The Oerlikon is a Swiss-designed gun made in the UK under license.
It was introduced into the Royal Navy in 1940.
Specifications of the Oerlikon anti-aircraft gun
Caliber: 20 mm
Barrel weight with the breech block: from 64 to 68 kg
Gun length: 2,210 mm
Ammunition feed: drum magazine holding 45, 60, 75, or 100 rounds
Rate of fire: from 250 to 320 rounds/min
The guns were fitted in single, twin, and quadruple mountings.
The gun is used for fast surface targets and for anti-aircraft as well.
So the gun was fitted to many, many naval ships:
from aircraft carriers right down to the smallest minesweepers.
In 1941, England commissioned battleship Duke of York
with six Oerlikon cannons on board.
It was the first British warship armed with Swiss anti-aircraft guns.
One of the key requirements that the British put forward for Oerlikons
was that they be operable and maintainable for unqualified personnel,
like fishermen and sailors from the merchant fleet.
This condition proved to be quite farsighted.
Before World War II kicked off,
Great Britain ordered 1,500 guns from Switzerland
and purchased a license for their production.
By 1943, single-barrel Oerlikon anti-aircraft guns were no longer effective
against fast and well protected enemy aircraft.
A good solution to this problem was the development of multi-gun mounts.
This is a 20-mm Oerlikon Mark 11 mounting, fitted with two 20-mm cannons,
each capable of firing up to 350 rounds/min per gun.
However, the magazine only holds 60 rounds,
so the rate of fire is dependent upon the crew’s ability to resupply magazines
to the gun throughout the action.
The twin mounts were fed with ammunition from the left- and right-hand sides.
To avoid mistakes during loading, the magazine for the left gun
was painted in a bright color.
This is the 60-round magazine, which fits on the cannon.
This one is empty, but it’s still very heavy.
Imagine it filled with 60 rounds.
It fits on the cannon like this,
and would be changed, perhaps, three or four times during an engagement.
The loader’s job is not just to load the magazine:
he has to put the bullets, or the shells, inside the magazine.
Each shell is individually loaded into the magazine pre-greased
to allow for lubrication through the firing system.
As you can see, the aimer uses his bodyweight to move the mounting in a training motion.
The elevation is adjusted by the hand wheel that you can see here.
When he is given the command by the gunnery controller,
and once he has got the gun onto the target, he calls
“Aimer, target!”
and is given the command to engage.
At that point, he takes the safety catch off
and fires the weapon.
When a shot is fired, gunpowder gases apply pressure to the projectile,
which starts moving out of the barrel, and the cartridge, which pushes the breech,
makes it slide along the barrel.
The weight of the breech and the return force of the spring,
pressed by it, are matched in such a way
so that the moment the projectile leaves the barrel,
a spent cartridge is ejected from the breechblock
and the next round is fed to her place from the magazine.
At this moment, the recoil spring pushes the breech back,
ramming the shell into the chamber.
There are two loaders for this gun: one for the right gun, and one for the left.
Obviously, they don’t just lift full magazines onto the gun
and take the empty ones away.
Their duties are also to act as the emergency crew.
Should anything happen to the aimer, he sits on the left-hand side,
then the gun can be fired manually by one person from the back of the gun here.
The guns in the twin mount fire in turn.
As a result, its cyclic rate of fire is about 600 rounds per minute.
The Oerlikon was used on ships as a short-range anti-aircraft gun.
Its effective range of fire was up to two kilometers.
You can say it was a last chance weapon,
especially for American ships,
as they had to face Japanese kamikaze attacks in the Pacific.
During the war, Oerlikon autocannons
were extensively installed on the ships of the Allies.
For example, the American Essex-class aircraft carriers
were equipped with up to 50 Oerlikon guns.
Therefore, the number of people on board the ships became significantly larger
due to the anti-aircraft gun crews.
Remembering that all the crew are actually linked together
by the gunnery control communication system,
they all can hear the commands from the gunnery director platform,
and the master gunner.
This box relates to the Type 6 gyrosight, and it’s the controlled inputs,
which are given to him by the gunnery director platform personnel
prior to the start of the engagement,
and sets such things as wind speed, direction, and air temperature,
which affect the ballistics of the ammunition.
If during the engagement, which obviously is very noisy,
there is a need to stop firing,
the gunnery director officer in the gunnery director platform
will press the check fire bell, which operates this bell you see here.
And this rings continuously until the aimer replies through his communication system
“Check! Check! Check!”
which informs the gunnery officer that he has stopped firing.
During World War II, the Allies produced over 300,000 Oerlikon cannons.
Many of them were later modified and upgraded,
but, in general, they still remained a Swiss design.
The gun was too advanced for the time when it was developed in the early 1930s;
and only when World War II broke out, did this cannon occupy a niche
where it was unmatched on both opposing sides.
According to US statistics, from December, 1941, through September, 1944,
as many as 32% of all Japanese aircraft were shot down by naval Oerlikon guns.
In the second half of 1942, about 48% of enemy aircraft losses
resulted from the use of these small-caliber cannons.
After the war, the 20-mm Oerlikon AA gun
remained in service with many navies around the globe,
until it was inevitably replaced by more advanced systems.
However, even today, you can still see the WWII-design Oerlikon guns
installed on some small patrol ships.