British/French WW2-era 0.5in Aircraft Machine Guns.

[xylstra]

It has always been a subject of some controversy as to why the British stuck with the rather paltry 0.303in calibre for aircraft machine guns. To address this Both BSA and ROLLS-ROYCE developed a 0.5in calibre AMG, the latter apparently quite successful (though strangely, never adopted) and the former developed years before the war for flexible mounting. But I understand that there was also another collaborative effort between France and Britain to jointly develop a 0.5in calibre aircraft weapon. I don't know the details, does anyone? I can only speculate that perhaps Hispano-Suiza may have been involved but over to you...... and what was its fate or was it merely a paper design exercise?

 

[Hood]

There is an article on this topic in Aviation Historian (Issue 40), The Missing Link? The French Connection by Matthew Willis.
The article is about the Anglo-French Permanent Executive Committee on Supply & Production which in February 1940 agreed the 13.2mm Browning FN should be the common medium calibre machine gun for both air forces.
Basically an admin misunderstanding between both caused delays ad by then Belgium was overrun (and then France) before anything could be done to set up a production line. By that time the .303in Browning was in high demand for fighter production and nothing further was done. Though as Willis says, Britain did keep the 0.5in Browning AN/M2 on its US orders and the North American Mustang was also specified with such weapons.

Few British types were actually modified for .50cals though, only the Spitfire with the 'E' wing and the Fulmar Mk.2 NF.

 

[CJGibson]

The Rose turret, fitted to later Avro Lancasters, also used the M2 Browning.

Chris

 

[SeaslugMk2]

Rolls-Royce modified their 0.5" HMG to use 0.55" Boys ammunition, but I've never been able to find out much of this weapon. The only file I found at the TNA in a search for 'Rolls Royce' and 'gun' gave me a single file...which was a couple of sheets referring to a pillar drill ordered in the States for the 40mm gun, and as the project had been cancelled asked if it should still be shipped across?

SRJ.

 

[xylstra]

Rolls-Royce modified their 0.5" HMG to use 0.55" Boys ammunition, but I've never been able to find out much of this weapon. The only file I found at the TNA in a search for 'Rolls Royce' and 'gun' gave me a single file...which was a couple of sheets referring to a pillar drill ordered in the States for the 40mm gun, and as the project had been cancelled asked if it should still be shipped across?

SRJ.

Hi SRJ. I read a summary of the ROLLS-ROYCE 0.55in development on an interesting page on Tumblr and it stated that the 0.5in calibre prototype performed flawlessly but the up-gunned 0.55in version for some reason had a dismal performance. the subtlety of ballistics!

 

[xylstra]

There is an article on this topic in Aviation Historian (Issue 40), The Missing Link? The French Connection by Matthew Willis.
The article is about the Anglo-French Permanent Executive Committee on Supply & Production which in February 1940 agreed the 13.2mm Browning FN should be the common medium calibre machine gun for both air forces.
Basically an admin misunderstanding between both caused delays ad by then Belgium was overrun (and then France) before anything could be done to set up a production line. By that time the .303in Browning was in high demand for fighter production and nothing further was done. Though as Willis says, Britain did keep the 0.5in Browning AN/M2 on its US orders and the North American Mustang was also specified with such weapons.

Few British types were actually modified for .50cals though, only the Spitfire with the 'E' wing and the Fulmar Mk.2 NF.

Thanks Hood. I think your reply is pretty much the full answer to my post and is entirely consistent with the little information I started with. Bit of a mystery why the British couldn't have just taken a short-cut by copying the German Mauser MG151, in war-time there would have been no commercial scruples about giving the two finger salute to licensing issues and of course, the Germans would have effectively, paid for all the development costs.

 

[riggerrob]

The British Royal Air Force may have started WW2 with .303 Browning machine guns, but as soon as they could, they installed 4 x 20mm cannons in most of their fighters: Hurricane, Spitfire, Typhoon, Tempest, etc. .303 calibre may have been potent enough to knock down fabric-covered biplanes, but was soon rendered obsolete by the all-metal airframes of WW2.
Vickers also developed a .50 caliber machinegun. Starting in 1932, Vickers .50s were issued to British Army light AFVs and the Royal Navy where they primarily served as AAA, typically in quad mounts. During WW2 they were replace din AFVs by 15mm Besa heavy machineguns. The Vickers HMG was a water-cooled behemoth weighing 63 pounds plus another 10 pounds of water. Vickers developed their own cartridge which was 12.7 x 81mm versus the Browning 12.7 x 99mm.

OTOH The Boys .55 anti-tank ammunition was never used in machineguns.

 

[CJGibson]

Bit of a mystery why the British couldn't have just taken a short-cut by copying the German Mauser MG151, in war-time there would have been no commercial scruples about giving the two finger salute to licensing issues and of course, the Germans would have effectively, paid for all the development costs.

Xylstra said this, not Hood, but I can't delete the quote. Anyway...

I'm sure someone will put me right, but aside from the Jerry Can and irregular picking up of the MP40 and other small arms by squaddies, I can't think of any piece of German kit that was officially adopted by the Allies during the war, never mind the British. An example of why not is the MG42. Apparently the sound of an MG42 invited a mortar/artillery barrage, so the Allied forces left them alone and continued with Bren and BAR.

a few Panthers were used, but was that official or just curiosity?

Anyone think of anything?

Chris

 

[Colonial-Marine]

Bit of a mystery why the British couldn't have just taken a short-cut by copying the German Mauser MG151, in war-time there would have been no commercial scruples about giving the two finger salute to licensing issues and of course, the Germans would have effectively, paid for all the development costs.

Xylstra said this, not Hood, but I can't delete the quote. Anyway...

I'm sure someone will put me right, but aside from the Jerry Can and irregular picking up of the MP40 and other small arms by squaddies, I can't think of any piece of German kit that was officially adopted by the Allies during the war, never mind the British. An example of why not is the MG42. Apparently the sound of an MG42 invited a mortar/artillery barrage, so the Allied forces left them alone and continued with Bren and BAR.

a few Panthers were used, but was that official or just curiosity?

Anyone think of anything?

Chris

The US Army had a company reverse engineer the MG42 for production in 30-06 but they forgot to account for some dimensional change and as a result the end product was horribly unreliable.

Captured 20mm Flakvierlings (and probably the single 20mm Flak guns) were popular enough where a manual in English was published for them IIRC.

 

[JWilly]

It was a major strategic screw-up on the part of the French and Belgians in the mid 1930s, and the British if they wanted a common gun too, not to financially encourage Fabrique Nationale to build a second factory complex in the south or southwest of France, far from a potential German invasion, and move their most-militarily-critical weapons production there...in return for substantial contracts to supply Britain and France with aircraft and AA HMGs based on the 13.2mm FN-licensed version of the Browning 0.5 inch HMG.

As noted elsewhere, the external dimensions and control mechanisms of the FN 13.2mm HMG were identical to those of the 0.5 inch version, and the ammo chutes and weight were essentially identical, so the guns were interchangeable. So, a single FN secondary factory well away from the very exposed Herstal headquarters location would be acceptable because US production capacity for the 0.5 inch version would be the redundancy/backstop. And, aircraft designed in USA and purchased by France or Britain would be able to be easily fitted with 13.2mm guns, and if needed or desired at a later date, switched back to 0.5 inch caliber.

The problem, I think, was with French politics. France's governmental system in all respects was, bluntly, an ineffective mess during all of the 1930s.

 

[Fluff]

Bit of a mystery why the British couldn't have just taken a short-cut by copying the German Mauser MG151, in war-time there would have been no commercial scruples about giving the two finger salute to licensing issues and of course, the Germans would have effectively, paid for all the development costs.

Xylstra said this, not Hood, but I can't delete the quote. Anyway...

I'm sure someone will put me right, but aside from the Jerry Can and irregular picking up of the MP40 and other small arms by squaddies, I can't think of any piece of German kit that was officially adopted by the Allies during the war, never mind the British. An example of why not is the MG42. Apparently the sound of an MG42 invited a mortar/artillery barrage, so the Allied forces left them alone and continued with Bren and BAR.

a few Panthers were used, but was that official or just curiosity?

Anyone think of anything?

Chris

Tangentially, only the 7.92 mg, used in tanks. Origin was Czech, so German ammo could have been used. Italian tanks were used in the desert, but not officially.

Really, the allies, especially USA, simply outproduced the axis, so whatever you wanted, it was easier to get the part number, and order it.

 

[Hood]

Time just ran out on the whole thing.
They didn't decide they needed a common set of machine guns to go alongside the common HS-404 cannon until Feb 1940.
Bureaucratic misunderstanding wasted until May when Belgium was overrun. From the article it sounds like the plans and some tooling made it to France but.... they only had a couple of weeks left before they too were overrun.

I suppose in an ideal world you might do an "Mr Foreman Goes to France" and snatch the tooling from Herstal and load it on a British destroyer or fishing boats, but alas timing didn't allow it.

Perversely, even if there had been a second production line up and running by early 1940, with France and Britain more excited about the HS-404 (and the teething troubles with feeding) there might not actually have been anything ready to use the guns on. Existing fighters would need an element of redesign, not to mention gun turrets and doubtless Beaverbrook would still want to stop production in favour of .303s that could be used in every RAF aircraft.

It's a bit harsh to blame French procurement of the 1930s for this one; they were quite happy with 7.5mm and 20mm as their favoured mix, a mix that was shared with the RAF and the Luftwaffe too (I don't think any German aircraft had 13mm at this stage). The US, Japan and USSR adopted a more tiered approach, the first two going for 7.62/7.7 and 12.7-13mm and the Soviets going for everything (7.62, 12.7, 20, 23mm).
If anything the late adoption by France and Britain was more due to frustrations with the 20mm, and as I say the aircraft designers had been tinkering with 20mm armed fighters since 1937 but hadn't given much thought to 13.2mm (I think perhaps Estonian Spitfire Mk.Is being the only exception).

 

[JWilly]

It's a bit harsh to blame French procurement of the 1930s for this one

A further factor was that the French already had a 13.2mm HMG in production, by Hotchkiss. It was used for naval AA, airfield AA by AdA (France had a very goofy split of land AA responsibility among multiple organizations), and was prototyped for vehicle mounted AA by the Infantry. The Hotchkiss gun was magazine fed rather than belt (a fundamental design error it had in common with the Hotchkiss 25mm autocannons), and was a bad enough design that it was mechanically limited on cycling rate rather than thermally, so was not suitable for aircraft use. But those details were irrelevant to the French government, which would not consider buying from FN because French workers already were making "the same" weapon and everything was about maximizing employment in existing French companies.

As noted in other posts, FN had developed in the late 1930s an explosive 13.2mm round that they had shown via testing to be very effective against aluminum-skinned aircraft...arguably even more so than 20mm because of the greater RoF and therefore likely greater number and location of hits. FN however found it very difficult in the sociopolitical environments and military stress of that period to get objective consideration of their weapon system. If I recall correctly, they had made two tentative sales, to Romania and Sweden. I don't know if any sales got as far as deliveries.

they were quite happy with 7.5mm and 20mm as their favoured mix, a mix that was shared with the RAF and the Luftwaffe too

Yes, but.

France and Britain were partnered in the French British Purchasing Commission, actively seeking to spend large amounts of French and British funds to buy USA manufactured warplanes among other weapons. US aircraft designs were transitioning in the late 30s from .30 caliber MGs...with mounting locations, controls and feed arrangements that with some trouble could be converted to .303 or 7.5mm...to .50 caliber. It wasn't practical to convert .50 caliber mount locations to .303 or 7.5mm, and it certainly wasn't practical to convert them to 20mm. So there was an awareness that any aircraft they bought after the P36 generation (i.e. the French H75) would be engineered for .50 caliber armament. The FN-made Browning 13.2mm was a drop-in replacement for the US Colt-made Browning .50 caliber (i.e. 12.7mm). Nothing else available to Britain or France would have offered that assured functionality.

So notwithstanding that they were "happy", they should have been aware that change was coming, one way or another.

 

[Fluff]

Time just ran out on the whole thing.
They didn't decide they needed a common set of machine guns to go alongside the common HS-404 cannon until Feb 1940.
Bureaucratic misunderstanding wasted until May when Belgium was overrun. From the article it sounds like the plans and some tooling made it to France but.... they only had a couple of weeks left before they too were overrun.

I suppose in an ideal world you might do an "Mr Foreman Goes to France" and snatch the tooling from Herstal and load it on a British destroyer or fishing boats, but alas timing didn't allow it.

Perversely, even if there had been a second production line up and running by early 1940, with France and Britain more excited about the HS-404 (and the teething troubles with feeding) there might not actually have been anything ready to use the guns on. Existing fighters would need an element of redesign, not to mention gun turrets and doubtless Beaverbrook would still want to stop production in favour of .303s that could be used in every RAF aircraft.

It's a bit harsh to blame French procurement of the 1930s for this one; they were quite happy with 7.5mm and 20mm as their favoured mix, a mix that was shared with the RAF and the Luftwaffe too (I don't think any German aircraft had 13mm at this stage). The US, Japan and USSR adopted a more tiered approach, the first two going for 7.62/7.7 and 12.7-13mm and the Soviets going for everything (7.62, 12.7, 20, 23mm).
If anything the late adoption by France and Britain was more due to frustrations with the 20mm, and as I say the aircraft designers had been tinkering with 20mm armed fighters since 1937 but hadn't given much thought to 13.2mm (I think perhaps Estonian Spitfire Mk.Is being the only exception).

And the British Army did the same, moved to 20mm Polsen etc. Royal Navy did use the 0.5 for ack-ack, but the Navy was always weird.

 

[Tony Williams]

It has always been a subject of some controversy as to why the British stuck with the rather paltry 0.303in calibre for aircraft machine guns. To address this Both BSA and ROLLS-ROYCE developed a 0.5in calibre AMG, the latter apparently quite successful (though strangely, never adopted) and the former developed years before the war for flexible mounting. But I understand that there was also another collaborative effort between France and Britain to jointly develop a 0.5in calibre aircraft weapon. I don't know the details, does anyone? I can only speculate that perhaps Hispano-Suiza may have been involved but over to you...... and what was its fate or was it merely a paper design exercise?

The reference you want is Rolls-Royce Armaments by D. Birch, published by the Rolls-Royce Heritage Trust in 2000. An excellent book, it goes through the R-R heavy machine programme in detail.

As far as Vickers HMGs are concerned, this web article probably tells you a lot more than you need to know:

 

[xylstra]

It has always been a subject of some controversy as to why the British stuck with the rather paltry 0.303in calibre for aircraft machine guns. To address this Both BSA and ROLLS-ROYCE developed a 0.5in calibre AMG, the latter apparently quite successful (though strangely, never adopted) and the former developed years before the war for flexible mounting. But I understand that there was also another collaborative effort between France and Britain to jointly develop a 0.5in calibre aircraft weapon. I don't know the details, does anyone? I can only speculate that perhaps Hispano-Suiza may have been involved but over to you...... and what was its fate or was it merely a paper design exercise?

The reference you want is Rolls-Royce Armaments by D. Birch, published by the Rolls-Royce Heritage Trust in 2000. An excellent book, it goes through the R-R heavy machine programme in detail.

As far as Vickers HMGs are concerned, this web article probably tells you a lot more than you need to know:

Thanks for the response unfortunately the second link doesn't seem to work. Are you able to re-send it as plain-text?

 

[HoHun]

Thanks for the response unfortunately the second link doesn't seem to work. Are you able to re-send it as plain-text?

On the Internet Archive:

Untitled Document

 

[xylstra]

Thanks for the response unfortunately the second link doesn't seem to work. Are you able to re-send it as plain-text?

On the Internet Archive:

Untitled Document

Thanks for that, the revised link worked great. Very informative web article it was too. Cheers.

 

[Nik]

IIRC, wasn't realised how rapidly the tempo of air-air combat would change. Remember, this was the era of 'turret fighters' that would merrily cruise along below hapless bomber streams, rend them 'by the numbers'...

Except bombers became faster than those 'turret fighters', and had front-firing fighters as outriders...

Also guns+ammo were large and heavy: So, multiple 303 plus 'lots' of ammo, or fewer, but harder-hitting 20mm with much less ammo ??

When was that famous 'Operational Analysis' done, that showed the optimal armament for mission-kill attacks by Hurri/Spits on fighters and bombers ? By the guy who co-opted his daughter, a brilliant teen mathematician ??