British .303 vs 50 Cal M2

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A reminder that P-47N's (Iwo Shima?) were fitted with M-3's toward the end of the war. 8 M-3's, I imagine, could put some hurt on a bomber of any size.
 
soulezoo said:
A reminder that P-47N's (Iwo Shima?) were fitted with M-3's toward the end of the war. 8 M-3's, I imagine, could put some hurt on a bomber of any size.
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Not really, no more than the Hurricane IIB (12 x 0.303) was deadlier to German bombers than the Hurricane I. Simply throwing more undersized rounds at a target doesn't really add much.
 
For what it's worth the Brits and Canadians both judged the value of the CF-100's eight centreline M3s as 'doubtful' (re: Bull, Bosun, Badger, Bison).
 
Even .303s don't "bounce" off.
Their ability to break large objects (wing spars for instance) is certainly limited but most engines that catch a 1/2 dozen or more .303 bullets are going to stop running after a few minutes. At least if the.303s are being feed proper ammo. No iron engine blocks on most aircraft engines (some Wright engines use steel crankcases) so at the very least you have coolant or oil leaks. Not to mention hits to "accessories" are not good.

The American .50 is an odd weapon in WW II, it was about the only weapon of it's size and weight that did not use HE ammo or even high capacity incendiary ammo. They started with incendiary available but phase it out when they adopted the M8 API round. Then they tried again with the really capacity M23 (or what would turn into the M23) but that ammo was highly unreliable (Drgondog's father seems to have had some tales about it lighting up right in front of the firing aircraft?). It probably depended more on kinetic energy than just about any other gun (only the Russian 12.7mm is in the same area and the Russians may have had better incendiary ammunition?)

The .303 in the BoB gets a bad rap for three things that were not it's fault.
1. The poor shooting in general of the British pilots.
2. The Air Ministries attempt/s to solve the first problem by pointing the guns in different directions so instead of concentrating at one distance and being spread at others it was spread at all distances.
3. An ammo shortage that had, at times, 3 guns out of 8 firing "ball" ammo intended for rifles or ground machine guns instead of AP or incendiary ammo.
 
Greyman said:
For what it's worth the Brits and Canadians both judged the value of the CF-100's eight centreline M3s as 'doubtful' (re: Bull, Bosun, Badger, Bison).
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When you get to jet bombers things take another change. The airframe and wing/fuselage skins you need to fly at 500mph are whole lot thicker/heavier than the ones needed for 300mph airplanes.

The two small Russian bombers weigh empty close to what a B-17E did empty. (the IL-2 is about 4,000lbs less) but the wings are about 1/2 the size, the Tu-14 has about the same length fuselage but the IL-28 is 16ft shorter, The VK-1 turbojet while heavy was certainly much lighter than two R-1820s.
This is empty weight so it had to go somewhere. Heavier stronger structure?
 

I think when pilots report rounds 'bouncing off' enemy aircraft it's probably due to striking the skin at very shallow angles and deflecting off.

Dowding himself considered it very fortunate that the Germans never armoured the rear of their bombers' engines - so that area with its 'mass of ancillary equipment' always remained vulnerable.


2. The big 'Dowding Spread/Horizontal Pattern' business was called off in Feb 1940 - so the battle was fought with the 'Concentrated Pattern'. The not-so-big 'Spread Pattern' came into effect mid-'42.

3. I think the ball rounds at this time were more by design than shortage. Dowding claiming that in tests the AP round was more easily deflected.
 
As far as 3 goes, that may depend on the test and the desired result or secondary target? Perhaps the AP did deflect more often but was the "ball" ammo (and was it MK VII or MK VIIIz ) with it's lead core going to have much penetration of a secondary target if it hit sideways? The "hardness" of many components once you got under the skin varied quite a bit. On some the ball ammo may have worked fine, on others perhaps the AP would have been better.
The AP was rated this way "For proof, 70% of bullets had to penetrate a 10mm plate at 100 yards range." which means that each production batch is going to have some cartridges taken out at random and fired to make sure the batch/lot was up to specification. Granted there is no intermediate barrier like an aircraft skin to tip the bullets before they hit the plate. Test firing was also done on the ground so velocity at impact will be bit higher at 100yds or more importantly, will retain velocity better at higher altitudes.
Later Spitfires carried two guns loaded with AP and 2 guns with Incendiary MK VI.
During the BoB it was reported that they used 3 guns with ball, 2 with AP, with incendiary/tracer MK IV and one gun with the Incendiary MK VI.
The incendiary/tracer MK IV carried 6 grains of white phosphorus and pretty much ignited on leaving the barrel. The longer it took to reach the target the less incendiary effect you were going to have. The Incendiary MK VI used 7 grains of SR 365 containing barium nitrate and did not burn in flight but bullets that broke up on the exterior of the plane would give a visible flash which was quite useful as a hit indicator.

A further note from Anthony Williams' book is that while they had decided in March (close enough to Feb) to use concentrated fire there was still dispute over the distance, Some squadrons using 350 yds and some 250yds. Dowding decided on 250yds in March but apparently not all squadrons changed as combat reports from June of 1940 showed the 53% success rate for the shorter distance vs 39% for the longer one. no mention of how "success" was measured.
decisions could be made high-up, how fast they were implemented by all squadrons might be different.
 

Dowdings orders were issued 23 Feb, so March is a good bet for implementation as well.

I have a copy of the June '40 report in question and it deals with the Horizontal Pattern (60 ft. wide box at 400 yards) vs. the Concentrated Pattern (single point at 250 yards) during the period 16 Oct '39 and 10 Apr '40.

Success was a bomber 'known to have been destroyed'.
 
I have the complete Hurricane II manual with the loading data.
Hurricane IIa 8x .303
guns and accessories 201 lbs, ammunition and boxes, 204 lbs = 405 lbs
Hurricane IIc 4 x20mm
guns and accessories 427 lbs, ammunition and boxes, 327 lbs = 754 lbs

additional info
1 x 20mm gun with firing unit 106.25, 100 rounds of 20 mm ammunition 62.5 lbs
1 .303 browning gun with release and safety units, 24 lbs, 100 rounds of .303 6.63 lbs
 
pinsog said:
I ...In Korea, didn't the USAF intercept a group of Soviet TU-4 bombers (B29 copies) and decimate them? Wouldn't they have all had 50's?
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IIRC Tu-2s twin-engine medium bombers, not Tu-4s. IMHO very improbable that Tu-4s would have flown in Korean airspace during the war. And yes the US fighters participating the action were armed with .5s
 
To get back to the original question. I had a feeling that we had answered this before. To quote Vanir in 2011
"Some comments on this by Sqn Ldr Ralph Sorley, FO1 of the Air Ministry in evaluation of fighter armament proposals for service use new British monoplane fighters (Spit and Hurri) in 1934.
(paraphrasing for space and clarity) "The choice lay between the .303 gun, the 0.50 gun and a new 20mm Hispano cannon. Of the .303 guns the result was the Browning from American Colt company appeared to offer the best possibilities. Given the numbers of stockpiled Vickers, the acceptance of a new gun in the numbers required was a heavy financial and manufacturing commitment. During 1934 the Hispano gun is experimental and confirmed details about its performance are hard to establish. The 0.50 on the other had had been developed little (in 1934) and although it possessed better hitting power it was a slow firing and heavy item together with its ammunition. A trial on the ground of eight .303 guns was sufficiently convincing and satisfying to carry the day."
.50 cal machine guns vs 20 mm autocannons on US aircraft

I am not totally convinced. It does seem that the RAF were happy to stick with the .303 because they were convinced by the late 30's that the 20mm cannon was the way to go.
This is a link to Colin Sinnott's book on Google books that may work!
The RAF and Aircraft Design, 1923-1939

It seems to indicate that all the RAF bigwigs in the late 30's were determined to get the maximum number of bullets fired in 2 seconds rather than worry about the "weight of shot".
Personnally, I think that they should have persevered with the 0.5 over the .303
 
From what I know the basic we will stick with 8 x 303 which was a very powerful battery in 1939, until the 20mm is fixed was the right approach. It came a little unstuck when the 20mm took longer to get right than first thought, but it was in my mind the correct approach.
It tends to be overlooked that the USN were very keen to supplement the 0.5 with the 20mm but it took the US until almost the end of the war to sort out the debacle that they made of the 20mm.
 

The thing was that the small Browning was pretty much ready to go. The British did modify to fire open bolt to prevent cooking off rounds with cordite propellent and no doubt would have had to do the same thing with the .50 cal.
Ammo for the .303 was pretty much a done deal, Ball, AP, tracer all existed along with a few specialty items (drill, proof rounds etc) although no one was very happy with the tracer/incendiary.
For the .50 things weren't so cut and dried. There was US ammo but it hadn't been "approved" by the British. Also please note, as has been mentioned before, that US .50 cal ammo in the 20s and 30s had muzzle velocity of about 2500fps. It took a change in propellent to give it the higher velocity that the US used in WW II.

In fact the US .50 cal cartridge had no velocity advantage to speak of over the British/Vickers .5 in machine gun cartridge, it did use heavier bullets.

For perspective here are the muzzle energies of the four rounds.

.303 AP, 174 grain bullet at 2500fps..................2415 ft lbs.
.5 Vickers AP, 580 grain bullet at 2540fps...........8308 ft lbs.
.50 cal AP M1, 750 grain bullet at 2500fps.........10408 ft lbs.
.50 cal AP M2, 710 grain bullet at 2810fps.........12447 ft lbs.

Now the .303 Browning fired just about twice as fast as the .50 cal Browning until some time in 1940. And the big .50 went just about 3 times the weight.

So the British would have had to "persevered" with the .50 by developing higher velocity ammo a the same time the Americans were and also increased the rate of fire of the gun and increased the belt pull.

How much engineering time to you devote to a gun and ammo that the British would only use (on fighters) as an interim gun until they could get the 20mm sorted out?
 
ChrisMcD said:
Given the numbers of stockpiled Vickers,
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As a digression. Does anyone know what was done with all these stockpiled Vickers? Lewis Guns turned up on ships and the Home Guard. Later Vickers Ks were employed in ground use and on small ships but I have never seen a photograph of any WW2 use of the Vickers bar in obsolete aeroplanes used for training or still in operational use (e.g Swordfish or Hart).
 

Lewises were used also to bolster the AA defences of the airfields, factories etc, IIRC at least some Vickers mgs were used for ground defences (against possible para or air landing troops attacks) of air fields.
 
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Finns replaced the P36 engine cowling guns 12.7mm (one or two), wings 7.5mm are replaced by 7.7mm guns. (some planes, not all).
I do not know why not used the German 7.92, maybe was it impossible to place it on the wing? Or was 7.7 still more efficient?
 

7.7 mm Browning was a standard FiAF gun, so Finns used them, ammo and spare parts supply was in place, why to acquire one more 7.5 - 8 mm mg?
 
I disagree, the canon heating, anti jamming problem was resolved way before the 20 series was produced. Infact the Hurricane and Spitfire had these freezing/gun jamming problems as early as the mk 1 browning .303 machine guns but was sorted out pretty quickly. So im not sure where this information is coming from.....
Plus the Hispano 20mm cannon were actually very reliable. From the Mk V onwards.
 

They might have been stripped for parts for Army guns or even rebuilt into watercooled guns during the Invasion panic post Dunkirk.
 
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