UK goes all-in on a HMG class gun in the mid-30'ies

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z42 said:
The shotgun argument was that a dense pattern was better because it would give a higher probability of a hit than with a slower firing battery of heavier guns.
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The Germans lost crews, a lot of very experienced crews because of those 8 .303's, they may not have the punch to defeat armour but hosing down a fuselage full of aircrew is a good substitute.
 
The Belgians did build two Hurricanes with 4 x .50 mgs. They did not see any combat though.
Imho the. 8x .303 armament has been over harshly criticised over the years. Between the hurricane and the spitfire they shot down thousands of ea with the"pea shooters". In the early war years limited to about 1000 hp engines, weight creep was a big problem with all fighters. For comparison the 8 .303 armament in the hurricane weighed 405 lbs including 330 rpg and all feeds and boxes. Comparable weight for 4 x .50 in an F4F with 4 x .50 and 200 rpg s 528 lbs.
 
slaterat said:
Comparable weight for 4 x .50 in an F4F with 4 x .50 and 200 rpg s 528 lbs.
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RAF is not obliged to us American guns and ammo. British .50 ammo, like the 12.7x80mm, was lighter than US .50.

slaterat said:
Between the hurricane and the spitfire they shot down thousands of ea with the"pea shooters". In the early war years limited to about 1000 hp engines, weight creep was a big problem with all fighters.
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Hurricanes and Spitfires were powered by at least 1300 HP engines in the early years of the ww2.
 
tomo pauk said:
RAF is not obliged to us American guns and ammo. British .50 ammo, like the 12.7x80mm, was lighter than US .50.



Hurricanes and Spitfires were powered by at least 1300 HP engines in the early years of the ww2.
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From late 1939 when 100 Octane became reasonably plentiful 1300 HP was available, but the RAF started experiments with 20mm cannon in 1940 with one squadron trying them in the BoB. The 20mm cannon was sorted by 1941 and was standard fitment for Mk II Hurricanes and Mk V Spitfires. I dont understand the point that is repeatedly made, which force wasnt using a mix of rifle calibre and something heavier in 1940/41?
 
The British bombers may (repeat may ) have benefited from an HMG.
They spent a lot of time trying to figure out how to mount four 20mm cannon in rotating turrets and it did take quite some time to put even a pair of 20mm Hispanos in a dorsal turret.


The 20mm Hispano needed support part way out on the barrel, which made for a difficult mount and a lot of wind resistance (drag) when turned.

Trying to come up with 3 powered mounts (and not using one in the nose) could really escalate the weight.
Once they had sorted out the 20mm in fighter wings the HMG was rather redundant for the RAF fighters so it's window of opportunity (advantage) was short.
 
The guns weren't the problem it was the inability to hit the target first then the availability of effective ammunition second that was the biggest issue. There are many gun camera photo's and reels from the BoB showing pilots firing from hundreds of yards out, well beyond the effective range of the guns with minimal deflection, using bigger guns in that situation just means you miss with bigger bullets. This is a good example, a He111 500 plus meters out past 90 degrees deflection and the tracers are going behind the target,

compared to the Stuka, the pilot is right in behind him 200 meters out.
 
tomo pauk said:
RAF is not obliged to us American guns and ammo. British .50 ammo, like the 12.7x80mm, was lighter than US .50.
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Who said they were? Not I. The weight was for comparison purposes as stated.

tomo pauk said:
Hurricanes and Spitfires were powered by at least 1300 HP engines in the early years of the ww2.
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Only the ones modified to take 12 lbs boost as a WEP rating. When introduced into service neither Hurricane or Spitfire were capable of 1,300 hp.
 
slaterat said:
Only the ones modified to take 12 lbs boost as a WEP rating. When introduced into service neither Hurricane or Spitfire were capable of 1,300 hp.
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By the time of the BOB all were modified to use 12 lb boost and were equipped with the Constant Speed Prop which together made a huge difference to the performance of the Spits and Hurricanes.

Again a personal view. The decision taken by the RAF in 1938 to rely on a considerable no of LMG prior to the introduction of the 20mm was exactly the right decision given the circumstances of the time and I believe they get a lot of negative comments which are very unfair.

There are two main points for this
a) When the decision was taken there were no real alternatives if you are going to war in 1939. The 20mm were not really mature and the 0.5 M2 wasn't either.
b) No one had armoured their aircraft. An unarmoured aircraft without SS fuel tanks was very vulnerable to 8 x LMG. It didn't matter how big the aircraft you were almost certain to take significant damage and one decent burst could easily finish you off
 
slaterat said:
Who said they were? Not I. The weight was for comparison purposes as stated.
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No need to get upset
My point was that there were heavier ammo types, and that there were light ammo types, despite the nominal calibre being the same.

slaterat said:
Only the ones modified to take 12 lbs boost as a WEP rating. When introduced into service neither Hurricane or Spitfire were capable of 1,300 hp.
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Neither Hurricane nor Spitfire were introduced in service in the early war years.
In the RAF service, +12psi boost on 100 oct rating on Hurricanes and Spitfires was a rule in the early war years, not exception.
 
Decision to go for many LMGs on fighters dated much earlier than 1938 - talk winter of 1934/35?


Soviets were installing armor on their I-16 well before the ww2, and He 111 of BoB vintage was reported as having self-sealing tanks. Ju-87Bs also sported armor.
 
The whole discussion seems to be based upon the British doing something different to the USA and so the British obviously made a mistake. Care is always taken never to include dates, because the British had cannon in their fighters before Russia, USA and Japan entered the war. The Spitfire and Hurricane had cannon fitted two years before the oft quoted P-47 started operations in Europe.
 
In order to have guns and ammo available in quantity in the summer of 1940 the decision as to guns/calibers would have have been made in 1938 at the latest in order to get British plants built and into production.
The US built under 8,000 .50 cal guns in 1940. No help there, that includes the aircraft guns, the AA guns for the Navy (before the 20mm were being built) and the AT guns and AA guns for the Army.

We have been over this many times. The Ammo the US and the British were using in the .50 cal in the 1920s, 30s and 1940 was lower in veleocity than the ammo that was introduced during 1940/41. The US ammo used a heavier bullet but at almost the same veleocity as the British, Italian and Japanese .5in/12.7mm and Tomo is quite right, there was a marked difference in the weigh of the complete rounds.
The pre-1940/41 ammo did not have as great a difference in power compared to the B-I-J ammo to really justify the greater weight of the guns/ammo.

Likewise the Merlin was being 'developed' in late 1939 and 1940. While the constant speed props were only fully fitted in June (?) of 1940 (hundreds of 2 pitch airscrews converted on the airfields) the higher boost was being tested and approved in 1939 and was subject to fuel availability. The 100 octane fuel was not anywhere near the close run thing the propellers were.
A number of Planes had left the factories with CS props, but not all. BTW the Blenheim was cleared to use 100 octane for take-off and combat while using 87 octane for cruise so the higher power of the Merlin is not in doubt in 1940.

However that does not solve the need to get the guns into production before winter of 1939/40 or spring. You need hundreds of guns per month and you need to fit the guns at the factories, no taking out the .303s and stuffing .50s in their place (it is a lot easier to fit a smaller gun into the larger gun/s space).
1300hp engines in Jan 1940 (to pick a date) doesn't solve the problem of which guns to use in Jan 1939.

The Belgian guns in 13.2mm were made to work but again, they were late, The British had already built the British Hispano plant/factory, purchased and installed the tooling, hired workers and and were putting the initial test guns out the door when the Belgians announced their gun. The British don't have time to start over.
And the almost identical guns in the first American aircraft to show up were a nightmare. They did get them to run after months of work.
I have no idea what the Swedes and Finns did to their guns or what their failure rate was.
 
tomo pauk said:
Decision to go for many LMGs on fighters dated much earlier than 1938 - talk winter of 1934/35?
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You are correct the decision was taken before 1938 but the point still holds
tomo pauk said:
Soviets were installing armor on their I-16 well before the ww2, and He 111 of BoB vintage was reported as having self-sealing tanks. Ju-87Bs also sported armor.
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The I16 did have some armour behind the pilots seat but that was often insufficient, but the I16 was the exception and not the rule.

By the time the BOB was being fought a number of aircraft had armour and effective SS tanks, but not when the war started and as you rightly pointed out, the decision was taken well before the war started. When the war started to the best of my knowledge, no German or British aircraft had any real protection.

I believe the first RAF aircraft to have armour designed into it from the start, on the drawing board, was the much maligned Whirlwind.
 
Excellent point, ''if'' the British decided to use the .50 BMG in the BoB they would have lost, it's that simple. The first Hispano armed Spitfires were used by Number 19 squadron and the guns were so unreliable the Squadron leader demanded they be replaced with the .303's, if you look at the .50 cal they were declared not combat ready by the FAA when fitted to the Martlet and likewise not ready in the P40 by the RAF so the outcome would have been the same, lots of Spitfires flying around with jammed guns, furthermore how do you fit them in the wings, you need mounts, ammo trays from the factory plus refitting all the planes already in service, re-calibrate all the sights, teach the crews how to repair and service the guns plus you only have four fitted due to weight and those four guns fire at around 450 rpm, compared to eight .303's @ 1150, you don't have effective incendiary ammunition, the first decent .50 cal was by reverse engineering .303 De Wilde type, the AP was found to tumble after striking the outer skin in tests so no the RAF made the right choice, stick with the .303's, leapfrog the .50's and go all out getting the Hispano into service.
 
Greyman said:
the main issue being deflections of aircraft skin at shallow angles (ie: dead-astern shots).
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Sorry but I'm going to put this old wives tale to bed because many years ago I proved this wrong, I shot at an old Valiant bonnet with standard Mk7 ammunition on our farm from the shallowest angles possible and all the bullets dug in, the shallower the angle the longer the groove cut in the bonnet so the damage increased the flatter it got, and it wasn't light alloy but sheet steel. Standing the bonnet up the bullet made a tiny .30 cal hole, laying it flat the same bullets made a 6''-7'' long tear.
 
An extract from Flying Guns: World War 2:

In addition to these problems, the actual performance of AP projectiles in battle can vary considerably from that achieved on test. In particular, passing through the thin aluminium aircraft skin can induce yaw, i.e. disturb the straight flight of the projectile away from travelling point-first, so that it fails to hit the armour head-on, thereby significantly reducing its penetrative abilities. In fact the degree of obstruction caused by aircraft structures is such that armour much thinner than theory indicated would be necessary was often found to give satisfactory results.

The most exhaustive tests during the Second World War seem to have been carried out in Germany. Official penetration curves for 7.92 mm AP rounds tested in 1942 are worth examining in detail because they reveal the variations which can occur. The SmK-v (Spitzgeschoss mit Stahlkern verbessert; improved pointed bullet with steel core) achieved the following:

at 100 m: 12 mm / 90º, 8 mm / 60º, 3.5 mm / 30º

at 300 m: 9 mm / 90º, 6 mm / 60º, 3 mm / 30º

at 600 m: 6 mm / 90º, 3.5 mm / 60º, 1.5 mm / 30º

However, if the bullet first penetrated a 3 mm dural (light alloy) aircraft skin angled at 70º, armour penetration at 100 m dropped to 4 mm / 90º, 3 mm / 60º and 2.5 mm / 30º.

A different 7.92 mm AP loading, the Pz-v (Panzerdurchschlagsleistung verbessert; improved armour penetration) penetrated less than 11 mm / 100 m / 90º but was much more tolerant of unfavourable circumstances, achieving 9 mm / 60º and 4.5 mm / 30º. Even more significantly, after penetrating the same angled dural skin the Pz-v could still penetrate 8.5 mm / 90º, 7 mm / 60º and 3 mm / 30º. Clearly, bullet design made a huge difference.

These results are supported by tests carried out by the British in January 1941 to compare British and German rifle-calibre steel-cored AP ammunition. The performance of the .303" (11.28 g at 735 m/s) and the 7.92 mm (of unspecified type, but measured at 11.53 g at 788 m/s) was first tested against "homogeneous hard armour". The thickness necessary to achieve immunity from this ammunition at 183 m was 12.0 mm for the .303", 12.5 mm for the 7.92 mm, when striking "at normal" to the armour (i.e. at 90º). The British ammunition was significantly worse when the striking angle changed to 70º; only 6.6 mm was needed for immunity in comparison with 8.9 mm to protect against the German round.

The test then changed to shooting at the rear of the long-suffering Bristol Blenheim at the same distance, involving penetrating the rear fuselage before reaching the 4 mm armour plate protecting the rear gunner, which was angled at 60º to the line of fire. The results in this case were reversed; 33% of the .303" rounds reached the armour and 6% penetrated it. In contrast, only 23% of the 7.92 mm bullets reached the armour, and just 1% penetrated. The British speculated that the degree of stability of the bullets (determined by the bullet design and the gun's rifling) might have accounted for these differences.

The Germans helpfully tested other nations' ammunition as well, and this produced some surprising results. They rated the British .303" AP as capable of penetrating 9 mm / 100 m / 90º, but only 2 mm after first penetrating the angled dural skin (which contrasts sharply with the results the British observed). Comparable figures for the Soviet 7.62 mm API were 10.5 mm and 4 mm, but the API/T fell to a maximum of just 6.5 mm; the steel AP core was lighter as the tracer used up some of the space (a common disadvantage of small-calibre AP/T bullets).
 
Glider said:
a) When the decision was taken there were no real alternatives if you are going to war in 1939. The 20mm were not really mature and the 0.5 M2 wasn't either.
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The previous discussion in this thread seems to suggest that indeed, there was no really good and mature HMG caliber gun available in the mid-30'ies when the decision would have needed to be made. However, on the cannon front, it seems the Oerlikon 20mm family was available and fairly mature by then, and had Britain chosen the FFL instead of the Hispano they could likely have 2x20 + 2x.303 armed Hurricanes and Spitfires if not at the start of the war then at least in time for the BoB.


With cannons, a "decent burst" could easily finish you off, with or without armor and SS tanks.
 
While there was a lot of interest in the Oerlikon guns actual interest in the guns as sold was not great. Rumania and Turkey (?) seem to be the biggest purchasers aside from France. France used the larger version in an engine mount, the others used the wing cannon.
Germany spent a while modifying them and spent several years trying to get them to work as a through the hub motor-cannon.
Japan purchased a license and then spent a few years turning it into the type 99 cannon.

A British attaché had seen the Hispano demonstration in 1936 and negations began shortly after. The Hispano offered a higher firing rate and more velocity.
Negations were slowed down by a number of provisions in the contract, like Marc Birkigt being a part owner of the British company/factory (10% of the stock with less than 50% being British held) . Also the British company was licensed to make a variety of Hispano Suiza products, like engines, buses, bicycles, speedboats, dirigibles, etc. . None of these options were take up. Birkigt didn't trust the British as an earlier deal to build H-S engines under license in Britain had fallen through which slowed things down. However the deed of partnership was registered in Britain on Jan 11th 1938.

The US placed an order for a trial gun plus ammo on July 27th 1937 with a delivery requested of Nov 11th 1937. The gun, after a 50 round test, was loaded aboard the U.S.S President Roosevelt on Feb 27th 1938. This was gun No 1027, serial numbers started at No 1000 to avoid confusion with the Hispano built Oerlikon guns. The first 20 guns went to France and the next 6 went to Britain.

I do not have a good time line on the Oerlikon guns but the available and fairly mature might be called into question considering that H-S only got into the cannon business back in 1933-34 with Oerlikon's slow delivery of cannon ordered the the French Air Force. Promising and delivering seem to be a bit different for both companies.

The British Navy had placed an order for 1500 big Oerlikons in the first 1/2 of 1939 but only 109 had been delivered by the time France fell and deliveries were cut off.

z42 said:
With cannons, a "decent burst" could easily finish you off, with or without armor and SS tanks
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This assumes that
1. You are at close range as the short 20mm Oerlikons had a higher time of flight than even .303 bullets and you need more lead.
2. You held fire until you were at close range so you weren't out of ammo when you got to close range.
In British service the .303 guns would fire almost 3 times longer than the German or Japanese short 20mm guns with their 55-60 round drums.
 
The British banked on the Hispano and that was very nearly ready for the BOB, being common fairly soon after it. The FFL was an inferior weapon to the Hispano so in my mind the decision which had to be taken before 1938 to go for an interim heavy battery of 8 x LMG was the right one.
z42 said:
With cannons, a "decent burst" could easily finish you off, with or without armor and SS tanks.
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True of course. But only if your 20mm are available and on this note its worth remembering that quite a surprising number of the Bf 109's used at the start of the BOB only had 4 x LMG. Now if the Germans who had bet the farm on the 20mm FF couldn't get all their fighters equipped with the 20mm. It would be wrong to assume that the UK could do any better with the FFL which was a later design. There is a good chance that the RAF introduction dates for the FFL and Hispano, wouldn't have been much different.
 
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