A basic primer on WW II aircraft guns

Shortround6 said:

Thank you, choice of which Oerlikon or moving to the Hispano seems to depend on timing and perceived need. Might also depend on purchasing countries industrial state.
I would note that the Germans had a least two cannon they were trying out in the mid 30s and I have no idea when work started on the MG 151.

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The RhB MG 204 was trial in a few aircraft and used a 20 x 105mm cartridge. The RhB MG C/30L was supposed to have trialed In Spain in a He 112 but as this was a lightened version of the standard 20mm AA gun using a 20 x 138mm cartidge it was large, heavy and slow firing. There are also claims that the MG 151/15 was trialed in Spain. Two years before it was installed in the He 115 float plane let alone the Bf 109F.

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Adoption of the Oerlikon FF was to speed up development/get something into service before the German programs came to fruition?

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Shortround6 said:

To avoid clogging other threads I thought I would try to collect the basic differences of WW II aircraft guns in one thread.
Books can and have been written on this subject so this is not an in depth study.

Breaking down the guns into 4 categories.

1, Rifle caliber machine guns. 7.5-8mm
2, Heavy machine guns 12.7-13.2mm
3 20mm cannon.
4 larger than 20mm cannon.

Of the Rifle Caliber Machine Guns (RCMG) most can be lumped together on this basic level.
No major country used a gun under 7.5mm in aircraft despite what their ground troops used which simplifies things.
Most of the guns were similar in size and weight which also simplifies things.
Rate if fire is the only big difference and if we take out the WW I left overs (Lewis guns, etc) and the two really high rate of fire guns, the German MG 81 and the Russian ShKAS then everybody else's RCMGs fall into the 900-1200rpm range which really simplifies things on this basic level.

So, RCMGs, not much difference in power (compared to bigger guns), not much differnce in size/weight and not a lot of difference in rate of fire with the two exceptions above and the MG 81 was pretty much a defensive gun.

Going to the Heavy machine class there are only 4 basic cartridges and 3-4 basic mechanisms amongst the major powers.

German 13 x 64mm round, used by the Germans and Japanese.
British .5 in/12.7x 81 round used by the Italians and Japanese.
The American .50 cal/12.7 x 99mm round which was necked up to 13-13.2 and used by the French, Japanese and a few minor actors.
The Russian 12.7 x108 used by the Russians.

For guns you had;
The German MG 131.
The Russian Berezin UB (and variations)
The Browning used by most everybody else in a variety of chamberings (and a few sizes of gun).
Italians did use one of their own but only in flexible mountings in small numbers.

On a basic level this simplifies things as you have two small cartridges close to each other in power and two large cartridges also close to each other in power.
There is a considerable variation in gun size and weight with weights going from 17kg to 34kg. But excluding the MG 131 and one (or more ) Japanese Navy 13.2mm Brownings just about everything else was from 23-29KG for the bare guns.

Rates of fire (once you get past 1940) went from about 700 -1050rpm with the low being the Italian guns and the high being some versions of the Russian gun.

More later,
Please remember this is basic, there are exceptions to found in small quantities or at the very beginning or end of the war.

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Weltraum Affe said:

Nice short clean summary.
How about the cannons?

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