SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
Now this is FIRST CLASS trolling!
Why no heavier RAF machine gun calibres?
- Thread starter Admiral Beez
- Start date
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(my bold)
Having personal favorites is okay.
Throwing mud on what you don't like in order to make your favorite stuff is misleading.
Deleted member 68059
Staff Sergeant
- 1,058
- Dec 28, 2015
I`d like to know why the WW2 Rolls-Royce aircraft cannon project floundered.
Shortround6
Major General
We have been over the 1930s .50 cal stuff a bunch of times.
The US .50 from the 1920s to about 1940 was NOT the gun used in 1942, either the gun or the ammo.
For the gun, it would do 600rpm, on test (ground), using short belts and free firing (not synchronized). Now everybody's guns slowed down when synchronized. Some were worse that others and the US .50 was pretty bad. But comparing synchronized gun fire rate to unsynchronized is not quite fair. It does matter to the aircraft in combat but it is not quite the thing looked at in early tests. P-40 Tomahawks were pretty much relying four .303 guns in the spring/summer of 1941.
Now in 1940 the US figured out how to make the gun fire at about 800rpm (+ or - 50rpm) and they could change parts and bring old guns up to the new performance. A big Question, which I have never seen an answer to, is when the British got the new guns or the parts to upgrade the old ones.
But back to "the British shoulda done..................in 193X" it was the 600rpm (at best) or nothing.
Please note there was no change in weight between the guns (maybe a few ounces?)
Ammo
In or about 1940 (some of this stuff took a while) the US changed the bullet and the powder and got the muzzle velocity of the .50 to go from 2500fpm to 2880fpm. Be careful here as the .50 used two different barrels. There were .45in barrels using in the water cooled guns and (different barrel) in the air cooled ground guns. The Aircraft guns used .36in barrels and had bit less velocity. This change in propellent was used in number of US rounds. The Powder was slower burning and the pressure curve was different. You could NOT make the higher performing rounds without the new powder.
The old ammo used a 48.8 gram bullet at 2500fps (762ms) with a muzzle energy of 10,765fp (14595 joules). This is not only what the British tested in between war trials, it was what the British ordered in 1939-40-41, I don't know when the US started delivering the US spec ammo to the British under lead lease. British may have hesitated using the new powder and sending ammo with it to areas around the world.
Be careful with some accounts of these old tests because some modern accounts seem to plug in the data for the newer .50 ammo into the old reports.
The difference between the British .5 ammo and the US. 50 cal ammo was pretty much the difference in bullet weight between the wars.
Cartridge...............................Bullet grains/grams......................velocity fps/ms...........................................energy fp/joules
British .5.........................................580/37.6.............................................2540/774...................................................8310/11267
US .50cal M1................................753/48.8............................................2500/762................................................10,765/14,595
US .50cal M2................................710/46.0............................................2880/878................................................13,128/17,800*
* numbers may be a little high (?) fired from 45 in barrel?
At any rate the M1 ammo had about 81% of power of the M2 ammo the jump to the US .50 was not difference in the late 20sor early 30s that it was in 1941/42.
The US .50 from the 1920s to about 1940 was NOT the gun used in 1942, either the gun or the ammo.
For the gun, it would do 600rpm, on test (ground), using short belts and free firing (not synchronized). Now everybody's guns slowed down when synchronized. Some were worse that others and the US .50 was pretty bad. But comparing synchronized gun fire rate to unsynchronized is not quite fair. It does matter to the aircraft in combat but it is not quite the thing looked at in early tests. P-40 Tomahawks were pretty much relying four .303 guns in the spring/summer of 1941.
Now in 1940 the US figured out how to make the gun fire at about 800rpm (+ or - 50rpm) and they could change parts and bring old guns up to the new performance. A big Question, which I have never seen an answer to, is when the British got the new guns or the parts to upgrade the old ones.
But back to "the British shoulda done..................in 193X" it was the 600rpm (at best) or nothing.
Please note there was no change in weight between the guns (maybe a few ounces?)
Ammo
In or about 1940 (some of this stuff took a while) the US changed the bullet and the powder and got the muzzle velocity of the .50 to go from 2500fpm to 2880fpm. Be careful here as the .50 used two different barrels. There were .45in barrels using in the water cooled guns and (different barrel) in the air cooled ground guns. The Aircraft guns used .36in barrels and had bit less velocity. This change in propellent was used in number of US rounds. The Powder was slower burning and the pressure curve was different. You could NOT make the higher performing rounds without the new powder.
The old ammo used a 48.8 gram bullet at 2500fps (762ms) with a muzzle energy of 10,765fp (14595 joules). This is not only what the British tested in between war trials, it was what the British ordered in 1939-40-41, I don't know when the US started delivering the US spec ammo to the British under lead lease. British may have hesitated using the new powder and sending ammo with it to areas around the world.
Be careful with some accounts of these old tests because some modern accounts seem to plug in the data for the newer .50 ammo into the old reports.
The difference between the British .5 ammo and the US. 50 cal ammo was pretty much the difference in bullet weight between the wars.
Cartridge...............................Bullet grains/grams......................velocity fps/ms...........................................energy fp/joules
British .5.........................................580/37.6.............................................2540/774...................................................8310/11267
US .50cal M1................................753/48.8............................................2500/762................................................10,765/14,595
US .50cal M2................................710/46.0............................................2880/878................................................13,128/17,800*
* numbers may be a little high (?) fired from 45 in barrel?
At any rate the M1 ammo had about 81% of power of the M2 ammo the jump to the US .50 was not difference in the late 20sor early 30s that it was in 1941/42.
SaparotRob
Unter Gemeine Geschwader Murmeltier XIII
I read your posts. I remembered.
ThomasP
Senior Master Sergeant
Hey Snowygrouch,
Check out the RRHT book "Rolls-Royce Armaments". It does a good job of describing the development and timeline of their 40mm cannon.
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The FF cannon didn't work that's why they redesigned it into the FF/Modified, the ammunition isn't interchangeable between the guns. As for the .50 Cal the rate of fire was 450 rounds per minute, the ammunition was low velocity and they weren't reliable, like the FF they were found lacking in combat so once again both the guns and ammunition were modified/redesigned into what became the M2 variant, what part of any of that is misleading?.
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Yes, yes it did Grasshopper.
Vickers was somehow able to sneak info about about the 40mm aircraft gun spec before it was released to the various firms, and so were able to get a considerable head start. As it happened the 'S' was always ahead of the 'BH' at the various development milestones.
In the end the Vickers gun was officially selected for 'installational' reasons and because it was easier to produce.
All the official tests on the Rolls-Royce gun (including air testing in Hurricanes and Beaufighters) indicate that it was a satisfactory weapon.
A note about why the British stuck with the .303-in Browning in its power turrets and so forth. In 1940, the turret manufacturers, Boulton Paul in particular was investigating a .50 cal armed turret, but was told by Beaverbrook, (Minister of Aircraft Production) that the .303-inch turrets were being standardised on because of expediency. The haste at which the British wanted to get power turrets onto bombers was the key and reverting from production as it stood in 1940 by the turret manufacturers, Nash & Thompson, BP and Bristol would have disrupted production at a time when the RAF was introducing newer bombers such as the Stirling, Manchester and Halifax into service would have delayed them entering service in numbers. All the turret manufacturers investigated bigger calibre guns in their turrets, some of which carried over into later production models of existing aircraft and newer bombers. The Nash & Thompson rear turret of the Lancaster Mk.VII was fitted with twin .50s, while the Bristol mid upper turret on the Avro Lincoln had two 20mm Hisso cannon.
Lancaster Mk.VII armed with Nash & Thompson rear turret armed with twin .50s. The mid upper turret is an N&T turret retrofitted to this aircraft for museum purposes. Mk.VIIs originally had Martin mid upper turrets with twin .50s.
_ADP5014
Lincoln Bristol mid upper turret armed with two 20mm cannon.
Bristol B.17
Lincoln Boulton Paul rear turret armed with twin .50s.
BP Type D
Lancaster Mk.VII armed with Nash & Thompson rear turret armed with twin .50s. The mid upper turret is an N&T turret retrofitted to this aircraft for museum purposes. Mk.VIIs originally had Martin mid upper turrets with twin .50s.
Lincoln Bristol mid upper turret armed with two 20mm cannon.
Lincoln Boulton Paul rear turret armed with twin .50s.
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Dad's last aircraft KB.865 had the Glen Martin 250 mid upper turret, with 50 cal guns. Dad's mid-upper gunner mentioned this to me and sure enough he was correct. Sadly, I never asked him what he thought of it relative to the (edit, Fraer Nash) turret. The GM250 was situated over the bomb bay step, about 6' further forward. These Canadian lancs arrived in March,1945. I have no idea if it changed air-to-air combat significantly. I suspect not.
Jim
Jim
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M is for 'this version fires Mine shells', not for 'modified'. Mine shells were judged as better ones, and the FF/M was tweaked to fire the better ones.
Between the FF (and FF/M) and the British Hispano, the later was a less reliable cannon before late 1941.
Nobody found the FF as lacking in combat, these downed hundreds and hundreds of aircraft.
There was no Breda SAFAT M2, nor it was the Vickers M2. Both were firing much faster than 450 rd/min, and the MV was more than useful for air combat.
J.A.W.
Banned
Joyce was an overhyped booze-raddled blarney-merchant, who produced unreadable blather, mistaken by acolytes for a novelistic pioneer.
"Einstein did his best work as a patent clerk" - Dr Peter Venkman. He has been 'outed' as a plagiarist too, in recent times.
Look, seriously - my own 'stream of consciousness' style is hard enough - but I use commas/paragraphs & what-have-you, & you can too!
Shortround6
Major General
When you take a blowback weapon and change the bullet weight significantly they don't work.
The MG FF used 130-134 gram projectiles at about 600m/s, very close to Japanese type 99-1 performance.
The MG FFM used 92 gram projectiles at about 700m/s but the recoil impulse is different and to no ones surprise they were not interchangeable.
The MG FFM also used a 115-117 gram projectile at about 585m/s that would function because it had a similar recoil impulse.
The MG FF worked fine with the original ammo. It needed lighter recoil spring and maybe a change in recoil mass (?) to work properly with the light Mine shell.
As as been stated other places, the .50 would fire at 600rpm when unsynchronized. The Velocity was about the same as both the British .5, The British .303, the Italian/Japanese 12.7mm, the later German 13mm, and it was only about 40-50m/s slower than the French, Italian, Japanese navy 13mm ammo. Reliability in aircraft did take some work.
The work was going on before they were used in combat. The work on the ammo had been going for period of time, just like the change from the old .30-06 ammo to the new M2 .30 cal ammo. The new M2 ball fired a similar bullet to the old 1906 load but did it at 42,000pis instead of 50,000psi with the new powder.
Work on the rate of fire was going on in 1940, very few of the US supplied aircraft had gotten into combat in 1940. Not the Tomahawks, not the P-39s, not the Buffaloes (at least in British hands).
You can argue all you want but the guns were modified, you either fired one type of ammunition or the other, they were not interchangeable. Also if the original guns were satisfactory they wouldn't have needed ''better ones'' would they and then be replaced by the MG 151 on all 109 models thereafter.
I'm talking about the M2 browning not a Breda or Vickers. In 1939-40 the RAF wouldn't have had the M2 model because it wasn't available, only the original model and original lower velocity ammunition.
None of the newer guns and ammunition were available in 1940 except the FF FF/M and even then just under half the 109's that fought in the BoB were low dash Emils with four 8mm MG's. The question is why the RAF didn't use heavy MG's in their aircraft, the simple reason is oth the .50 BMG and Hispano needed an equal amount of work so why choose the smaller gun.
If there was a possibility to improve, people were willing to do it.
MG 151 fired perhaps zero shots in anger in 1940, while the MG FFM was actually there and doing it's job. It was still in wide scale use in 1943.
I was replying on what you've actually wrote, not what you've thought you wrote.
Not the case, the .50 was passed over because it needed just as much development as the Hispano while offering lower performance, sorry but that's a fact.
Which 50 cal? In 1940 it wasnt what it became in 1943/4. They cause different damage. In 1940 RAF pilots were being struck and damaged by single rounds from 20mm cannon while seeing German bombers sail through hundreds of hits by their 0.303 mgs. Post war it was found that although many bombers didnt go down straight away, they ditched or made forced landings with dead or injured crews, by mid September 1940 what was th most formidable airforce in the world was down to its last 200 serviceable bombers and crews.
