20mm ammo against WWI planes


#1

I’ve been going through my 20mm’s and thinking…hmmm. If 20mm was developed during WWI to shoot down aeroplanes, would not it be a major overkill since the planes flew low’n’slow and were not protected very well? Or someone actually had visions of huge “flying tanks” clad in inches of steel?


#2

The only 20mm gun which made it into service in WW1 was the Becker, which seems mostly to have been fitted to aircraft - either for bomber defence or ground attack.

If you’re a bomber gunner and a front-engined fighter is flying straight at you, then you really want to smash up the biggest target - the engine - as soon as possible.

By the end of the war, armoured ground-attack planes were in service, so again the ground-based guns would have been useful in the AA role. Don’t forget that the Becker was nothing like modern 20mm AA guns; it had a low muzzle velocity and would only have been effective in the AA role at fairly short range.


#3

I would also add that by the end of the war large well defended strategic bombers were coming into service that could absorb a great number of hits from rifle calibre guns. Britain had the Handley Page 0/400 and the Germans the Giants and Gothas.

We did not go down the 20mm route, prefering to develop a .5 inch weapon and the .600/.500 round that eventually became the .5 Vickers. However, thoughts were turning to larger calibre guns like the COW gun and Vickers 1 Pdr and 1 1/2 Pdr.

1918 aircraft were becoming a lot more sophisticated than many people realise.

Regards
TonyE


#4

We may also not forget the 20mm Erhard gun.

Also keep in mind that (from todays judgement by existing specimen) the most commonly used ammo in the 20mm Becker (and Erhard) was the “tracer” round. Today we would call it a TP-T.
I wonder if internatinal agreements on warfare (Geneva Convention and others) played a role since no HE/Frag projectiles with a weight below 1 pound were allowed against personnel. We may never find out.


#5

Although as Tony said aircraft and aircraft combat changed dramatically during WW1 but the strategy was alway ( I hate saying always on here because somebody always proves me wrong) to kill the pilot, an easy and vunerable target, and thereby bring down the plane. Sometimes they would get lucky and sever a fuel line etc but the pilot was always the principle target so it was an AP exercise and 20mm anything was un necessary.

The first attempt to bring down the ship rather than kill the pilot occoured with the Zepplins over London.

Fabric covered wooden framed aircraft were mostly fresh air and could take a lot of holes with nothing vital hit. It was extreme chance to hit something as small as a control wire


#6

I know that at least 51 Ehrhardt guns were made (because I’ve examined one with the serial number 51) but as far as I’m aware they never made it into service. I’d be interested in any evidence that they did.

[quote]Also keep in mind that (from todays judgement by existing specimen) the most commonly used ammo in the 20mm Becker (and Erhard) was the “tracer” round. Today we would call it a TP-T.

I wonder if internatinal agreements on warfare (Geneva Convention and others) played a role since no HE/Frag projectiles with a weight below 1 pound were allowed against personnel. We may never find out.[/quote]

Yes, it did play a role and both sides were rather nervous about it, but it was the existence of hydrogen-filled airships and tethered balloons for artillery-spotting which prompted the development of explosive/incendiary bullets. The British restricted their use to home defence against airships, because they were worried what might happen to any pilot captured with such ammo in his gun.

After the war an international convention of lawyers met to discuss revisions to the St Petersburg Declaration (which banned explosive/incendiary projectiles of less than 400 grams) and agreed that these should be permitted when used by or against aircraft. This was never formally ratified but everyone thereafter tacitly accepted it.

The last example of a gun which seems to have been designed to comply with St Petersburg which I am aware of was the USN’s 1.1 inch AA gun of the 1930s. This odd calibre just happened to produce a shell weight just over 400 grams.


#7

True in fighter-v-fighter combat, Vince, when they tried to get behind the enemy and shoot him in the back. Probably also true of fighter-v-bomber when the fighter pilot might well have aimed at the cockpit. However, it wasn’t fighters which carried the Becker cannon but bombers, mainly for defensive purposes. And if you’re a bomber gunner and a fighter is heading straight for you, the pilot is almost entirely concealed behind the engine (especially if it’s a radial) with only his head sticking out. Then you want to stop the engine…


#8

I know that at least 51 Ehrhardt guns were made (because I’ve examined one with the serial number 51) but as far as I’m aware they never made it into service. I’d be interested in any evidence that they did.
[/quote]

I do not have the evidence but would wonder how such a weapon made it to Belgium (in a Museum today) and also some ammo for the Erhard is coming from there and from France. I assume the Germans took it there before WWI ended.


#9

There’s an Ehrhardt gun in the Leeds NFC, too - there was a lot of interest in German armament developments among the allies after WW1, and I don’t doubt that they were seized from the Germans (aircraft armament being forbidden under the Treaty of Versailles).

The ammo is the kind of interesting, pocketable souvenir that gets taken home. After all, the 13x92SR was only used in a few anti-tank rifles, and look how common it is in collections today!


#10

Very interesting Thread! Thanks.

Lew


#11

The only serious effort, as far as I am aware, to arm a fighter for plane-versus-plane combat with a firearm of larger than small arm caliber was the SPAD XII, which was produced in a small series for the French air service. It was armed, as I understand it, with a single-shot 37 m/m cannon which fired through the propeller hub. With the geared Hisso engine it was possible to place the weapon in the vee between the cylinder banks and fire through the hub of the geared-down propeller. The ace Georges Guynemer had some success with this plane, but this probably due more due to Guynemer’s marksmanship than to the qualities of the armament. It was not generally regarded as a success. Jack


#12

The French were the pioneers in arming aircraft with cannon, usually fitted to two-seater planes, and made more use of them than anyone else, but as Jack says they were all large-calibre (37+mm) manually loaded guns.

There’s an article on my website on the early aircraft cannon and their ammo, here: quarry.nildram.co.uk/cannon_pioneers.htm