Impact of fully adopted and reliable 20mm in BoB

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Still relevant today, modern sniper ammunition as used by the British army is standard production ammunition, it is the first batch of ammunition made from new forming and reloading die's, the tighter tolerance is due to the tooling being brand new, nothing more.
 
stona said:
By coincidence retired British naval officers were on secondment in Japan with the Imperial Navy and reported to the Air Ministry on Japanese comparative trials of six contemporary machine guns. The Vickers came last, and by a long way.
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Hi
The Japanese solution to a Vickers replacement was was the 7.7 Type 89 Model 2 for the JAAF and the 7.7 Type 97 for the JNAF, which were in use during WW2. These are classed as derivatives of the Vickers, at least by Francillon in 'Japanese Aircraft of the Pacific War'.

Mike
 
The Basket said:
Not saying Spitfire shouldn't have ground attack but certainly saying that 20lb bombs are hardly ground attack.

I learnt something so happy with that. Didn't know about the specification to load 20lb bombs.

.
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Hi

The 20 lb bomb requirement did trigger some memories so I have had a look through some of my books:

'Curtiss Aircraft 1907-1947' by Peter M Bowers, mentions on p.479 reference the XP-40, which first flew 14 October, 1938 (so later than the Spitfire):

"Wing racks could be fitted for six 20-lb (9 kg) bombs."

'The Warplanes of the Third Reich' by William Green, in the data for the Heinkel He 112B-0, p.315 mentions that its armament included "six 22-lb, anti-personnel bombs on underwing racks."

It appears that a requirement for light bombs to to carried by fighters was not confined to the RAF!

Mike
 

The original Vickers-Berthier light machinegun was chosen by the Indian Army as their LMG because they got very tired of the almost endless British Army selection process. The British Army went to great lengths not to choose the VB, eventually choosing the foreign ZB26 which couldn't fire .303, being chambered for 7.92mm Mauser. This wasn't considered a problem as the British Army was actually considering switching to 7.92mm Mauser (as the Tank Corp did with the BESA), but then the rushed re-armament of the late-30s meant the ZB26 had to be redesigned to fire .303, becoming the slow-firing Bren.
The Vickers-Berthier light machinegun design was developed into the Vickers Gas-Operated (VGO) aircraft gun used by observers in such aircraft as the Fairy Battle, early Bristol Blenheim, Fairy Swordfish, etc. In the VGO, the gun used a 100-round pan rather than the 30-round magazine of the original gun. As the name implies, unlike the original Vickers (Maxim) design, the VGO was gas-operated rather than recoil-operated, and was very reliable despite having a rate-of-fire only bettered by the MG 42. Vickers did produce a 300-round drum for the VGO for use as a fixed wing gun, but the RAF decided they preferred the belt-fed Colt-Browning Star. The early Gloster Gladiators had two Vickers guns in the fuselage and two VGOs, the latter being one each wing in a pod underneath and only with 150 rounds each.
When the RAF started replacing their observers' guns with Brownings, they shifted the VGOs to airfield defense. A number were fitted with a bullpup stock, a pistol-grip and a bipod, and used as LMGs by the RAF Regiment. Some were later borrowed by the Royal Marines who wanted a medium machinegun lighter than the traditional Vickers for D-Day. The Marines loved the VGOs buzzsaw-like rate of fire, but found it hard to keep the guns fed when the guns could empty the 100-round pans far faster than the crews could reload the empty pans!
The most famous users of the VGO was the Long Range Desert Group and the SAS, who mounted them on jeeps for attacks on Axis airfields in the Western Desert. The LRDG tried all available guns, including Colt-Browning Stars, and found that the VGO fired faster and was more reliable than any other available gun, Axis or Allied.
If the VGO had of been designed with a belt feed then the British Army could have had an air-cooled, gas-operated, general purpose MG twenty years before the FN MAG, and the RAF would never have even tried the Colt-Browning Star, but Vickers were worried it would steal sales from their more expensive recoil-operated model.
 

Look at the top picture of L1750, the one of the front end of the gunpod from the starboard side. Look at the opening to the gunpod where the barrel extends out, do you see the spring that is tight around the barrel? See how the opening around that spring is much bigger than is required for the small spring? That's because that is a pic of the Hispano fitting, in the gunpod originally sized to fit the longer Oerlikon with the much larger recoil spring.
Then look at the bottom picture of the cannon with the gunpod cover removed. Notice how the support frame is much bigger than the width and depth of the Hispano? So much so it has an extra clamp attached to the frame to hold the Hispano in place. That's because it was originally sized for the Oerlikon.
As regards the V7360 serial number, I don't know if that was applied later. The original aircraft was a Hawkers private prototype, so it may have been bought over to the RAF as part of a later contract block. I do know for a fact that F/Lt. A.C.Rabagliati from No 46 Squadron was flying the 4-Oerlikon Hurricane I V7360, squadron identifier PO B, on the 5th of September 1940 and shot down a Bf 109 with it, it's reported in the official Squadron history for 46 Squadron.
 
The A&AEE trial I have on V7360 is dated 13 August 1940 which clearly states four Hispano cannon.

The whole purpose of this aircraft was to gain experience with Hispano guns while the prototype IIc (Z2326) was still in development.
 
Greyman said:
The A&AEE trial I have on V7360 is dated 13 August 1940 which clearly states four Hispano cannon.

The whole purpose of this aircraft was to gain experience with Hispano guns while the prototype IIc (Z2326) was still in development.
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The first four-Hispano-armed Hurricane wasn't built until January 1941 due to a shortage of cannon. By August 1940 the deliveries of Hispanos MkI cannon from BMAR Co were prioritised for Bristol Beaufighters, so much so that 12 Group even considered removing the cannons from the few cannon-armed Spitfires with 19 Squadron and sending them to Bristol. This would have been popular with the 19 Sq pilots as they considered the Hispano MkI completely unreliable and claimed that not one pilot managed to shoot all sixty rounds in a drum without a jam, even when flying straight and level. Production of Hispano MkIIs used by the Hurricane IIC didn't even start until January 1941.
The big difference between the MkI and MkII Hispano was that the chamber was 2mm shorter to stop incidences of lightly struck primers. When the US started making Hispanos they ignored that update and went with the longer chamber, recreating the light strike issues that BMAR Co had already eliminated. With the shorter chamber the Hispano was finally judged reliable, and all MkIs in RAF service were retroactively modified in 1941.
Both F/Lt Smith and F/Lt Rabagliatti reported firing all ammunition without stoppages in combats in August and September 1940, which makes it so very extremely unlikely as virtually impossible that they were using the Hispano MkI cannons available.
If you want to state that V7360 was a summer 1940 Hawkers production block aircraft, it couldn't have been fitted with four reliable Hispanos for the simple reason that Hawkers didn't have any. That and because 151 Squadron started their trials with Oerlikon-armed Hurricanes on 23rd March 1940, which would seem to pre-date your August test by a almost three months. There is also the problem with operational dates - 151 Squadron left 11 Group to go on rest to Digby on September 1st 1940, and we know that F/Lt Roddick Smith had already flown the four-cannon V7360 in combat before they went on rest. That would mean he was flying the aircraft at the same time your report says it was at A&AEE.
So, for your timeline, we have an aircraft that flew in combat before it was built, was tested whilst assigned to an operational squadron, then magically jumped back to an operational squadron (46 Sq) in time to have another successful combat on 5th September 1940, all whilst Hawkers didn't have any Hispano cannon required to get the reliability results obtained. Oh, unless it was armed with Oerlikons.
 
Mad Dog said:
The early Gloster Gladiators had two Vickers guns in the fuselage and two VGOs, the latter being one each wing in a pod underneath and only with 150 rounds each
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The underwing guns were Lewis mkIII guns not Vickers. Late production Gladiators had 4 Browning's which fired at a max of 1100 to 1200 rpm the Vickers gas operated fired at a max of 950 to 1050 rpm.
 
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Greyman said:
The A&AEE trial I have on V7360 is dated 13 August 1940 which clearly states four Hispano cannon.

The whole purpose of this aircraft was to gain experience with Hispano guns while the prototype IIc (Z2326) was still in development.
Click to expand...

If it was a prototype then it wouldn't be part of a production block because production builds come after you have tested and finalised the design, which does suggest the serial V7360 was (a) a security cover, or (b) just Air Ministry accounting so that Hawkers could be paid when the airframe was taken on by the RAF.
As I pointed out, all the Hispano MkIs produced by the summer of 1940 had already been delivered to Westland for the Whirlwind or Supermarine for the 19 Squadron 2-cannon Spitfires, and new ones were going to Bristol for Beaufighters, and there were no Hispano MkIIs built yet. We also know the pneumatic cocking system adapted for the Hurricane MkIIC was tested with Oerlikons, which implied V7360 had Oerlikons both in action and in testing.
Below is a pic of the Japanese Type 99-2 20mm cannon, which was almost identical to the Oerlikon FF-L tested by the RAF. Note the much bigger recoil spring around the barrel and the larger shroud. Now, look at the pic of the Hispano in the L1750 gunpod and compare that shroud to the size of the opening on the gunpod - you can see how the gunpod was designed to fit around the Oerlikon's shroud, hence why it appears a loose fit to the Hispano. Then go back to the test pic of V7360 - see how the shroud around the cannon on V7360 are larger than the production IIC shrouds, and that the barrels are longer than the Hispanos in L1750? That's because they are Oerlikons.
 
fastmongrel said:
The underwing guns were Lewis mkIII guns not Vickers......
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Only the prototypes and a very few early production RAF Gladiators MkIs had Lewis wing guns, they were replaced with VGOs as soon as the VGOs became available. Unfortunately, due to delays in VGO deliveries, the most common armament for the first year of service was two Vickers MkV fuselage guns and empty gunpods!
Two fuselage Vickers MkVs and two VGOs were standard RAF Gladiator MkI armament until all four guns were replaced with Colt-Browning Stars. The fact the VGO looks similar to the Lewis means the "Lewis-gun-armed-Gladiator" myth endures, along with the "Lewis-gun-armed-Battle" myth, and the "Lewis-gun-armed-Blenheim" myth, etc., etc.
Below is a pic of a development Bristol turret with a Lewis aerial gun. Notice how the gas cylinder below the barrel goes almost all the way to the muzzle:

The VGO had a much shorter gas cylinder. Here is a pic of a Battle gunner with a VGO, notice the shorter gas cylinder:

Here is a pic of the Gladiator SS37 prototype with Lewis guns in the gunpods, note the gas cylinder under the barrel projecting almost to the muzzle:

Now look at any pic of an RAF Gladiator in service, the wing guns either have a long, smooth barrel with no gas cylinder projecting out of the gunpod (VGO):

or a fatter, jacketed barrel (see below) with a finned step near the muzzle (Colt-Browning Star):
 
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Greyman said:
Well, I welcome any evidence whatsoever that Oerlikon guns were put into a Hurricane.
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Did you not read any of the prior posts? Go on, just try explaining your pic of the L1750 gunpod with the gaping mouth so much bigger than required for the Hispano. Was it maybe so they could also vacuum up any ducks they came across in flight?
 
Mad Dog said:
Did you not read any of the prior posts? Go on, just try explaining your pic of the L1750 gunpod with the gaping mouth so much bigger than required for the Hispano. Was it maybe so they could also vacuum up any ducks they came across in flight?
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My guess is for the Hispano's front mounting unit.

Example pictured below is not necessarily the exact setup in V1750. There were quite a few different mounting arrangements.

 
Mad Dog said:
Below is a pic of a development Bristol turret with a Lewis aerial gun. Notice how the gas cylinder below the barrel goes almost all the way to the muzzle:
Click to expand...

Your point about the Lewis is sound but the photo is of a Type G.43 cine gun.
 
The F4?F's or F6f's had six fifties, where two could be shut off. I didn't know they had any serious problems?
 
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