Why the heck did they design it that way?

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David Fred said:
The MkIa had a Rotol Constant Speed 10'9" prop.
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ANd when did they get them?

The first 77 (?) Spitfires got the wooden 2 blade fixed pitch airprops, then they changed to the DH 3 blade two pitch prop. and there they stayed until the late spring of 1940. They trialed the Rotol prop in the fall of 39. but actual production started when?
from June24th to Aug 16th 1940 there was a mad scramble to refit all the Spitfires and Hurricanes with two pitch props to constant speed operation. This could be done using a new pump/controller on the engine and a new cockpit control using the existing propeller. However this more than bit late to also try changing the armament of the existing fighters.
 
Well, until you get your hands on Allen's book, there isn't much more to discuss.
His idea wasn't to re-equip existing fighters, he says the RAE and Air Staff made the wrong decision to begin with. That Four .50 BMG would have been a better choice, and provides RAE test data comparing the energy delivered (minus the gram or so explosive in the .50 API round, kinetic energy only). And the .50 would exact a weight penalty of 36 kg, but the Mark 1a had more horsepower.

I took his test data, and just multiplied it, i.e. 8 .50's would deliver twice the energy, 6 would be 1.5 times. He doesn't say what methodology was used for the tests, but it's not relevant, as the test conditions were the same for all weapons. I built the attached table.

Look, I don't have a horse in this race. I don't care. I thought this site was about information exchange, not pissing contests. I'm only telling you what one senior RAF officer says in his book, and it is clear that 4, or even 2 Hispano 20mm cannon are superior to both, especially for bomber work, if for no other reason than around 10 grams of explosive per round.

I tried to find a pdf file to send, since a lot of that stuff is out there now. No luck, and I didn't want to have knock on my door about copyright infringement,

At any rate, I have offered all I can on the topic. Make of it what you will.
 
You can print in multi color or tuttie-fruttie.
You can print it large font or huge font.

It doesn't change the fact that
The numbers are wrong.

Mistake #1
The Muzzle velocity of the .303 MK VII ball was 2440fps not 2240.

See: .303 inch Ball Mark VI to VIIIz & L1A1 - British Military Small Arms Ammo

Or most any other website.

That changes the energy to about 2300ftlbs per round.

Mistake #2

The numbers for the .50 cal ammo are wrong for the the 1930s and 1940.
The US M1 Ball and M1 AP used a 750 grain (48.6 gram ) bullet at 2500fps.

That changes the ME to 10,407ft pounds from the listed 13,250ft pounds.

Again see .50 inch Browning Ball - British Military Small Arms Ammo

I also have ballistic tables and penetration tables for .50 cal ammo using this weight bullet and velocity as published in "Ammunition" By Melvin Johnson and Charles Haven. This is the same Melvin Johnson who designed the semi-automatic rifle and LHG that bear his name.
The lighter bullet/higher velocity round (the M2 ball and M2 AP) did not exist during the times the RAF were evaluating the .50 cal gun before the war and in fact the it was the heavy bullet/lower velocity round that the British purchased in 1940 for the .50 cal guns they did have. The M2 ammunition required a different formulation of powder than than the M1 rounds used.

Without Dr Who and a Tardis (time machine) there is simply no way around this problem.

Mistake #3 The pre war guns didn't fire at the rate of fire given in the book (which I do have, I just hadn't read it before some of the initial posts)
The Pre war guns fired at best at 600rpm (using short belts, long belts slowed them down) and even the later guns are listed in the manual (April 1942 publication date) as firing 700-850rpm. Taking the highest possible figure is not making a fair comparison.

Mistake #4. The M8API round with the 1 gram of incendiary material (not explosive) Doesn't show up until 1943. An incendiary round (M1 incendiary) was available sooner but NOT at the time of the BoB. This round contained about 2.5 grams of incendiary material but again, no service .50 cal round carried explosives.

The Air Ministry did make a lot of mistakes, failing to use a time machine to bring back weapons and ammo from the future was not one of them.
 
Wow. The RAF must have had some pretty shitty senior officers, as the numbers came straight from his book.

You should have higher standards.
 
I can't help it if he is wrong.

His numbers (except for the MV of .303 and the average rate of fire for the M2 ) are actually correct for guns and ammo form around late 1941-42.

Just because he made wing commander doesn't make him the 2nd coming of Moses coming down from the mountain with tablets from God.

Look up the numbers for yourself.
 
David Fred said:
as the numbers came straight from his book.
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Ever thought an author might be trying to sell his book. There's nothing sells better in Britain than a book that makes us feel good about losing the 2nd world war and able to blame some high ups for the disaster that was the Battle of Britain.

Seriously though this book is just one of many that tells one version of history. Never rely on one book or one point of view, read a range of books or articles by different authors. Even do a bit of research it's not that hard most of the records are available. I recently spent two weeks off sick looking up figures of losses and victories for the Battle of France for all combatants and never left my bedroom.
 
David Fred said:
Wow. The RAF must have had some pretty shitty senior officers, as the numbers came straight from his book.

You should have higher standards.
Click to expand...
I can see from this attitude, that you're not even willing to listen to facts, even though they have politely been repeated in clear and accurate detail.

Just because something comes from a book, doesn't mean it's 100% accurate. If so, then we should believe such things as Green's myth that a Ju390 flew to the east coast of the U.S. - which facts proved it didn't.

Just as now, facts (from several solid resources) are proving that there's errors in the books you're using as a basis for your argument.

Perhaps take a little time to check those sources provided and be better informed?
 
Any number of books, instruction manuals and websites will confirm the 2440fps velocity from the .303 cartridge MK VII from Lee-Enfields, Bren guns, Lewis guns, Vickers guns and others. They all had 24 in barrels give or take an inch or two. Why the Browning aircraft gun would loose 200fps of velocity from the same length barrel defies belief.
 
I came here late for the current argument over the number of angels who can dance on the head of a pin/MG performances.

The situation at the point pre war when the RAF was looking at something better than the .303" was that the Browning 0.5", at that time, was not a class improvement over the multi .303" weight for weight. Better yes but not in another whole class. The 20mm cannon however was in a different class and they made a very reasonable decision, at the time, to skip the 0.5" and go straight for the 20mm cannon. You can argue the detail of each class's performance but they still fall into the same three classes.

Whatever the 0.5" Browning may have become later on they had no hindsight to employ and made a quite proper decision.

BTW had they wanted to go to a 0.5" Browning (probably in 13.2mm form) it may well have been via FN a short ferry ride away rather than with Browning themselves across a whole ocean.
 
Going to the 13.2mm just means screwing up the supply chain.

British are going to adopt an American cartridge (for which exist several production lines, that may or may not be involved in a European war) or French/Belgian cartridge, with fewer/smaller production lines that have the possibility of being cut off? (Belgian if not French?)
 
Is it known when the Air Ministry decided to pursue the Hispano as a replacement/compliment to the .303? Must have been in the late 1930's, as they were being trialed in 1940
 
The British MARC company deed of partnership was filed Jan 11, 1938.
It was established with a capital of 100,000lbs.
The title deeds for the plots of land for the factory were recorded in June of 1938.
Machinery was purchased in Britain and the United States.
At the official opening on Jan 1939 the Duke of Gloucester fired the first British HS 404.

Which really points to when/how they could have squeezed in the .50 cal Browning.
 
And HAD the HS 404 been successful in a wing mount installation in 1940, the question of why they never selected the .50 M2 would be even less realistic. Considering as well, that the .50 was also initially troublesome in wing mounts. And was mounted in the engine cowl, in single installations at that time
 
What supply chain? If they chose 13.2mm the supply chain would be all 13.2mm. The production would be in the UK for both gun and ammunition and FN can supply the tooling designs. Not hard. Even the Swedes made a 13.2mm. I am not advocating FN over Browning I just mention that they are closer and used to dealing with similar clients.There are issues over sizes, material and stock sizes and machining practices to be worked out in taking on any foreign gun but this did has never deterred the British. They did the Bren gun the hard way converting Czech metrics etc. to UK standards which took too long so they simply made the BESA in metric just as the Czechs designed and made it complete with 7.92mm ammunition. There was no assumption that an RAF Browning 0.5" gun would be made the same as the USA ones nor that the ammunition would be coming from the USA. The .303" differed from the us design and used British ammunition.
 
The British got hundreds of thousands of rifles and millions of rounds of ammunition in the first World War, in addition to artillery guns and ammunition and great quantities of other goods/military equipment.
I find it hard to believe they would abandon that supply source.

The Americans had gotten burned in the first World War when they did join in with too many factories geared up to make foreign weapons/ammo that the US did not really want and was forced to improvise weapons to make do with what was in production.

If Britain had no supply chain (factories with tooling for .50 cal ammo) and was creating a new one do you go with the European caliber or for the American caliber?

I would also note there were several problems with the .50 or 13.2 mm guns as they stood in the late 30s. Actual performance may not have lived up to advertised performance (it didn't on the American guns anyway, cycle rate rarely matched the book rate).
Once the Americans pushed the cycle rate to 700-850rpm the gun became a real barrel burner. The April 1942 manual calls for firing a 75 round burst and then waiting a minute before resuming fire at one 20 round burst per minute. If you waited 15 minutes you could fire another 75 round burst.
In Synchronized guns where the gun was pre-heated by the engine the manual recommends a 50 round initial burst and 15-20 rounds per minute after that.
If no long initial burst was fired then the manual says 25 rounds per minute can be fired for long periods of time.

Now in combat you do what you have to do and barrel life may not be big consideration but raising the cycle rate on a gun like this is just going to make the problem worse and do it much faster.
At some point in 1944 the US was chrome plating the interior of the barrels and/or using stelite inserts to combat barrel wear.

Obviously an April 1942 manual was written without the benefit of much (if any) combat experience (and pease remember that the AA guns were water cooled and the ground guns used a much heavier barrel).
 
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