# Why did the RAF persist with the .303 throughout the war?



## CobberKane (Jul 24, 2013)

This one has doubtless come up before, but what the hell. By the end of the BoB it was - from all accounts - pretty obvious that the Browning .303 lacked the firepower to reliably deal with increasingly tough LW fighters and bombers. The Hispano 20mm proved the answer. Yet the Browning persisted in conjunction with the larger gun on Spitfires, Mosquitos and Beaufighters. Why? Wouldn't ditching the Browning for half as many .50s or a couple of extra cannon have made sense? Or was there something about the way lots of small projectiles complemented the explosive cannon shells that that made the combination more than the sum of it's parts?


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## Ivan1GFP (Jul 24, 2013)

They DID ditch the .303 on the Spitfire which went to 2 x .50 cal and 2 x 20 mm.
Perhaps the high rate of fire was too attractive.

- Ivan.


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## beitou (Jul 24, 2013)

Didn't the Spits have a variety of wing fittings that included 303, .50 and 20mm. Later Uk fighters went for 4X20mm. Of course with the UK government one can never rule out cost as an issue but I hope it wasnt in this case?


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## Jabberwocky (Jul 24, 2013)

CobberKane said:


> This one has doubtless come up before, but what the hell. By the end of the BoB it was - from all accounts - pretty obvious that the Browning .303 lacked the firepower to reliably deal with increasingly tough LW fighters and bombers. The Hispano 20mm proved the answer. Yet the Browning persisted in conjunction with the larger gun on Spitfires, Mosquitos and Beaufighters. Why? Wouldn't ditching the Browning for half as many .50s or a couple of extra cannon have made sense? Or was there something about the way lots of small projectiles complemented the explosive cannon shells that that made the combination more than the sum of it's parts?


 
Economics.


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## stona (Jul 24, 2013)

They ditched it on all their fighters didn't they, moving to primarily cannon armament with some .50 cal machine gun. I'm thinking mid/late Mark Spitfires, Typhoon, Tempest etc. They were retained along with 20mm cannon on the Mosquito IIRC.

They originally went with the .303 for the rate and weight of fire that eight machine guns could provide (150 r/s and 1.8 Kg/s). The Air Ministry didn't have a high opinion of the ability of pilots to shoot accurately and there was much debate about which pattern would be most likely to result in hits (ie how to synchronise the guns). The Air Ministry was proven correct

The fact that .303 was the standard British and Commonwealth/Empire rifle calibre meaning there were literally millions of rounds available may have had something to do with it too, though how much of Major Dixon's redesigned De Wilde ammunition was available I don't know.

Cheers

Steve


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## Shortround6 (Jul 24, 2013)

A several sorts. 
The British had no production line/s for either the .50 cal Browning or it's ammunition. At certain times during (usually early) the war the US was in no position to supply large quantities even if the British had money or credit. 
The British .5 in Vickers gun was heavy, low powered, slow firing and less than reliable ( durable is another thing). The British would NOT mount a .303 Vickers gun were the pilot/crew could not get to it which is why they adopted the Browning. 

The .303 Browning weighed 10kg, the .50 Browning 29kg and the Hispano about 50KG. 
The ammo went about 24 grams for a .303 round, 112 grams for a .50 cal and about 257 grams for a 20mm Hispano. weights of links, ammo boxes, mounts and such can affect over all weight. 
The four .303s with 500 rounds each in a Mosquito weigh about 94.5 kg. That weight gets you TWO .50 cal Brownings with about 140 rpg. adding another 13-14kg gets you to 240rpg. Or ONE .50 cal with 480 rounds.
Going for the 20mm gets you ONE gun with 170-175 rounds? 
Granted you can increase the weight of armament installation in many planes. Power turrets needed to be redesigned to hold the .50s and the 20mm guns were a real problem, it was done but the 20mm Hispano was a very long gun and worked best with a support at the forward end of the receiver


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## Shortround6 (Jul 24, 2013)

stona said:


> They originally went with the .303 for the rate and weight of fire that eight machine guns could provide (150 r/s and 1.8 Kg/s). The Air Ministry didn't have a high opinion of the ability of pilots to shoot accurately and there was much debate about which pattern would be most likely to result in hits (ie how to synchronise the guns). The Air Ministry was proven correct



Air Ministry was correct in their opionion of the pilots ability but they didn't seem to devote a lot of time/effort to gunnery training. Some of the "patterns" the Air Ministry devised were less than ideal, too. 



stona said:


> The fact that .303 was the standard British and Commonwealth/Empire rifle calibre meaning there were literally millions of rounds available may have had something to do with it too, though how much of Major Dixon's redesigned De Wilde ammunition was available I don't know.



Not enough 

BoB mix usually had one gun in eight firing the Dixon/De Wilde ammunition. Later in the war the mix shifted to two guns out of four. In the BoB 3 guns out of 8 were firing "ball" ammo (rifle). The other guns were firing armor piercing and regular tracer/incendiary ammunition. Late war the ball and normal tracer disappeared. Two guns out of four had AP and two guns had Dixon/De Wilde which improved the effectiveness. Bomber guns used a different mix but the 'ball' ammo had disappeared from those ammo loads too.


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## Greyman (Jul 24, 2013)

CobberKane said:


> This one has doubtless come up before, but what the hell. By the end of the BoB it was - from all accounts - pretty obvious that the Browning .303 lacked the firepower to reliably deal with increasingly tough LW fighters and bombers. The Hispano 20mm proved the answer. Yet the Browning persisted in conjunction with the larger gun on Spitfires, Mosquitos and Beaufighters. Why? Wouldn't ditching the Browning for half as many .50s or a couple of extra cannon have made sense? Or was there something about the way lots of small projectiles complemented the explosive cannon shells that that made the combination more than the sum of it's parts?



As Jabberwocky said, it wouldn't be economical to undertake this massive .50-calibre endeavour for what is essentially a back-up gun. A back-up gun with a shrinking requirement and (according to British and American pre-war trials) pound for pound, lower destructive power.



stona said:


> They originally went with the .303 for the rate and weight of fire that eight machine guns could provide (150 r/s and 1.8 Kg/s). The Air Ministry didn't have a high opinion of the ability of pilots to shoot accurately and there was much debate about which pattern would be most likely to result in hits (ie how to synchronise the guns). The Air Ministry was proven correct





Shortround6 said:


> Air Ministry was correct in their opionion of the pilots ability but they didn't seem to devote a lot of time/effort to gunnery training. Some of the "patterns" the Air Ministry devised were less than ideal, too.



Pattern size and pattern density are inversely proportional. Of course everyone wants the largest possible pattern - but everyone also wants the pattern with the highest lethal density. There was _much _argument within the Air Ministry as to what the sweet-spot was.


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## Shortround6 (Jul 24, 2013)

Greyman said:


> Pattern size and pattern density are inversely proportional. Of course everyone wants the largest possible pattern - but everyone also wants the pattern with the highest lethal density. There was _much _argument within the Air Ministry as to what the sweet-spot was.



Not just the Air Ministry, the Navy quad .5 had each gun pointed to a slightly different place so that at any likely combat distance (plane is not crashing onto the gun mount) only one gun could hit a plane at time. Time needed to get a reasonable number of hits was way longer than the gun mount could track a target for.


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## pattle (Jul 24, 2013)

Don't shoot me down in flames over this, but weren't the 303s sometimes there mostly to sight the cannon?


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## Greyman (Jul 24, 2013)

Might have happened in some instances but for the most part; no. Definitely not in RAF doctrine/training.


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## Shortround6 (Jul 24, 2013)

About the only time .303 guns were used to "sight" cannon was on the Hurricane IID and IV with the 40mm guns. 

Once you get into longer ranges ( say 300 yds or more) the MG bullets will tell you where _should_ have been aiming 1/3 to 3/4 of a second _ago._ a 300mph airplane is covering 440 feet per second (133 meters). Maybe better than nothing but not really a big help and at close range you might just as well shoot everything all at once. 
Most combat bursts seldom lasted more than 2-3 seconds. Waiting to get the .303s on target, seeing the .303s hit and then trying to fire _before_ the .303s move back off target is too complicated and time consuming.


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## RCAFson (Jul 24, 2013)

I think the RAF would have been better served by adopting the Vickers .5" HMG:


> The RAF also evaluated the .5 inch Vickers and Browning guns. The results were inconclusive; the Browning was more powerful but was longer and heavier. It was concluded that the .303 inch version of the Vickers was almost as effective as the HMGs against the light, unarmoured aircraft structures of the time and it was much lighter as well as faster-firing. The RAF accordingly decided not to proceed with a heavy machine gun, while noting that any widespread adoption of armour for military aircraft would force a re-think. By the mid-1930s, when the increasing performance and toughness of aircraft began to cast doubt on the future of rifle-calibre guns, the RAF opted for the greater destructive power of a 20 mm cannon, choosing the French Hispano HS 404. A few American .5 inch Browning M2 guns were used late in the Second World War in applications for which the Hispano would have been too big and heavy, but apart from this no heavy machine guns were used by the RAF.
> Untitled Document



as it has much better range and AP performance than the .303 mg and is somewhat lighter than the Browning .5".


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## davebender (Jul 24, 2013)

I agree.

.50cal MG might be nice to have but Britain had more important things to spend resources on.


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## CobberKane (Jul 24, 2013)

The .303 was phased out of course, but not until after the war - right up to the final bell the British were churning out Spits, Beaufighters and and Mossies with the small Browning.
I can see how the .303 would have been the best choice at the time of the BoB, when planes had less armour and the rush to get as many fighters in the air as possible meant the RAF needed whatever was available in numbers and ready to go, but I'm surprised that after the US entry into the war there was (possibly) not the option of procuring guns from there. The Australians managed to get their hands on enough .50s to use them in place of the .303s in the Beaufighters they built - did they make their own? And while I can see the logic in retaining a gun that fired the same ammunition as infantry weapons, that didn't stop most of the other airforces from moving to HMG or cannon only armament - the imperative of having to tackle tough bombers, perhaps? And once the US entered the war the world would have been knee deep in .50 cal ammo, surely?
Overall, I can't see any insurmountable problem that would prevent the Brits dumping the .303 in favour of the .50 had there been sufficient motive to do so. The fact that they didn't suggests that, at least in combination with cannon, the rifle calibre guns remained useful weapons.


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## pinsog (Jul 24, 2013)

I never understood the British idea of pointing all of your guns in different directions. They were already using a popgun anyway, the only real way to make a 30 caliber weapon effective against airplanes is to point them all at the same place and get a good dense pattern on your target. Trying to shoot down an HE111 with one 303 while the other 7 shoot off into space had to be any excercise in futility and extremely frustrating for the British pilot. It would be like hunting geese with an open choked shotgun and #9 birdshot. Even if you hit him with a few pellets, the pattern isnt dense enought to cause enough damage to bring him down. 

On the other hand, if you have all 8 of them shooting into a 3 foot by 3 foot square at 100 yards, it would act like a buzzsaw. Each round itself is still underpowered, but in concentrated form it would still be MUCH more effective than only one gun being on target while the other 7 waste ammo shooting off into space.


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## beitou (Jul 24, 2013)

Were the aircraft with mixed armament able to select only the cannon or mgs or was there just one firing mechanism?


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## CobberKane (Jul 24, 2013)

pinsog said:


> I never understood the British idea of pointing all of your guns in different directions. They were already using a popgun anyway, the only real way to make a 30 caliber weapon effective against airplanes is to point them all at the same place and get a good dense pattern on your target. Trying to shoot down an HE111 with one 303 while the other 7 shoot off into space had to be any excercise in futility and extremely frustrating for the British pilot. It would be like hunting geese with an open choked shotgun and #9 birdshot. Even if you hit him with a few pellets, the pattern isnt dense enought to cause enough damage to bring him down.
> 
> On the other hand, if you have all 8 of them shooting into a 3 foot by 3 foot square at 100 yards, it would act like a buzzsaw. Each round itself is still underpowered, but in concentrated form it would still be MUCH more effective than only one gun being on target while the other 7 waste ammo shooting off into space.


 
I suspect the idea of being able to concentrate all the wing mounted guns into one small area might have been a bit of myth, at least in the case of the Spitfire, with it's armament spread across the wing. It might have worked in the butts, but in in flight wing flex and vibration would have dispersed the fire. Another incentive for ditching the .303s in favour of .50s mounted next the cannon, as happened with some late spits? 
I think pilots and ground crew were given a fair bit of latitude in how they set up their guns, too. Certainly BoB experience bought sighting ranges in significantly as a matter of policy.


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## swampyankee (Jul 24, 2013)

The 0.5 in Brownings were, at least according to one source I've read, installed because the 20 mm cannon were susceptible to freezing at altitude. They were not that much lighter than the 20 mm, and they were much less effective (the USN, apparently, found the 20 mm to be three times as effective in air-to-air combat than the 0.5 in Browning, but the US had problems with getting the 20 mm production sorted out)

I don't know why the RAF kept the 0.303 in service as long as it did; it seems that about the only thing it was good for by the end of the war was strafing troops in the open.


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## bobbysocks (Jul 24, 2013)

beitou said:


> Were the aircraft with mixed armament able to select only the cannon or mgs or was there just one firing mechanism?



usually they were able to select.


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## swampyankee (Jul 24, 2013)

pinsog said:


> I never understood the British idea of pointing all of your guns in different directions. They were already using a popgun anyway, the only real way to make a 30 caliber weapon effective against airplanes is to point them all at the same place and get a good dense pattern on your target. Trying to shoot down an HE111 with one 303 while the other 7 shoot off into space had to be any excercise in futility and extremely frustrating for the British pilot. It would be like hunting geese with an open choked shotgun and #9 birdshot. Even if you hit him with a few pellets, the pattern isnt dense enought to cause enough damage to bring him down.
> 
> On the other hand, if you have all 8 of them shooting into a 3 foot by 3 foot square at 100 yards, it would act like a buzzsaw. Each round itself is still underpowered, but in concentrated form it would still be MUCH more effective than only one gun being on target while the other 7 waste ammo shooting off into space.



According to information on Tony William's site, the RAF originally set the guns to converge at one point; after war experience they stopped doing so. Possibly, this was because aircraft were not point targets, and the bullets that missed the point of aim still hit other parts of the airplane.


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## Ivan1GFP (Jul 24, 2013)

Keep in mind the time period in which these fighters and their armament were chosen:

In the mid 1930s, the typical fighter armament was still only two or perhaps, if you were forward thinking, four rifle caliber machine guns. 
The Japanese kept this with their Ki-27 and even Ki-43-I fighters. 
The Germans only had 4 x 7.92 mm MG with the Me-109.

This wasn't quite as ineffective as a typical infantry rifle though. Most nations used different ammunition in their machine guns and especially aircraft machine guns. The ammunition was loaded a bit hotter and may have been armour piercing or incendiary / tracer as well. Funny thing was that although .303 Rifle ammunition still had Cordite as a propellant, the machine gun ammunition used a much less erosive propellant.

Also, except for MG ammunition intended for overhead fire for training, typical MG ammunition isn't all that accurate. So.... The idea of common ammunition between aircraft and infantry is not correct. Ammunition tends to be packaged for an intended weapon and used as packaged.
Folks don't break down 5 round stripper clips to load a MG belt or de-link a MG belt for infantry use.

Some folks, and I believe the British did this as well, harmonised guns in pairs so that the outboard guns converged a bit further out. The theory at the time expected fighter armament to be much longer ranging than 300 yards or less as it turned out in action.

The early 20 mm installations were VERY unreliable. Just about any G load from maneuvering while firing and the gun stops working. Also, the drums typically only carried 60 rounds or so. So, assuming everything worked, you only got about three good squirts from the cannon before they became dead weight. Later installations carried more ammunition, but that is what they started with in the first installations. 

The German and Japanese cannon at the time were no better and even had worse ballistics.

Also consider that armour was not installed in most fighters of the time.
Seems to me the .303 Browning MG was a pretty reasonable selection for the time.

- Ivan.


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## davebender (Jul 24, 2013)

Two centerline mounted machineguns (preferably .50cal / 13mm) is viable for shooting down fighter aircraft. I think that's why late war Me-109 kept the cowl guns even though they had cannon.


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## Greyman (Jul 24, 2013)

CobberKane said:


> I can see how the .303 would have been the best choice at the time of the BoB


It wasn't, and the first ones to tell you that would be the British Air Ministry. They chose the .303 Browning to replace the Vickers Mk.V in 1934. By 1937 they had already decided that the 20mm Hispano should replace it. But, you can't just snap your fingers and change something like that. Reality got in the way - right up until 1945.



CobberKane said:


> I'm surprised that after the US entry into the war there was (possibly) not the option of procuring guns from there.


It was possible, but the British didn't want it, for reasons already mentioned. They _were_ clamouring for more Hispano guns, which the US was trying to produce, but when the requirement for Spitfire guns was halved (the decision being made to only equip them with two cannon) the British could rely on their own production.



pinsog said:


> I never understood the British idea of pointing all of your guns in different directions.


The idea was '_is it wise to put all the eggs in one basket?_' If you miss (which most pilots did) you miss with all. It wasn't necessarily 'the British idea' either. Most Air Forces spread their guns somewhat.


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## Jabberwocky (Jul 24, 2013)

Economics was the prime driver, but institutional inertia, the early reliability of the Hispano and previous assesments of the .50 all helped the RAF to retain the .303, even when they knew it was comparatively ineffective.

The UK had the .303 Browning gun and .303 ammunition in production and had significant stockpiles of ammunition. The gun was cheap, reliable and until the introduction of increasing amounts of armour plate on German bombers, quite effective.

The RAF didn't think they neded a .50 cal class weapon. Their assesment of the .50 Vickers and (early) M2 Browning conducted in the 1930s found that the heavy machine gun was neither fish nor fowl: it didn't have the rate of fire or pattern density of the .303 nor did it have the hitting and explosive power of the larger cannon. 

In later trials against protected fuel tanks, the .50 cal rounds tested were more likely to penetrate and cause large holes, but were not that much more likely to start fires than the .303 (mostly due to the inadequate design of the early incendiary rounds). So putting many .303 rounds onto a target rather than fewer .50 cal rounds made sense, at least from the results of the trials.

The early Hispano had some reliability issues. These related to the all sorts of things, including lightly struck ammunition, the feed mechanism/magazines (about half of all stoppages were feed related), the gun mounting, the recoil springs, gun heating, ejection ports and fouling of the gun mechanism from grit/contamination. These were solved progressively through the war, but the RAF retained the .303s as a back up in case the 20 mm malfunctioned. 

Self-sealing fuel tanks and armour plate really only began to appear on German bombers from mid-1940 onwards. For the RAF to recognise the .303 is less than wholly effective takes time. Then they have to decide to do something about it, actually do it and then distribute the solution. All that takes a while. Some pilots still favoured the .303 over the cannon well into 1941.


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## pinsog (Jul 24, 2013)

The idea was '_is it wise to put all the eggs in one basket?_' If you miss (which most pilots did) you miss with all. It wasn't necessarily 'the British idea' either. Most Air Forces spread their guns somewhat.[/QUOTE]

But that doesn't make sense. A few random bullets from one rifle caliber machine gun is unlikely to bring down an HE111, DO17 or JU88. I understand that many British pilots during the BoB were not well trained, especially in gunnery and that they had to get REALLY close to hit anything. But again, pointing all of your guns in different directions will not give you enough damage for a kill. What is the point of aiming each gun in a different direction just to be able to claim you hit an aircraft? "Hey guys, I put 20 bullets into a German bomber today. It will take them at least 10 minutes to patch that up when they get back" If you are going to shoot at enemy bombers, your goal should be to destroy them, not hit them randomly with a dozen or so bullets while your other guns are blazing away off in a different direction. Also, if you are going to close to less than 50 yards on an enemy bomber, which untrained British pilots often did, you should be able to hit it with your guns concentrated in a small target area.


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## Shortround6 (Jul 24, 2013)

Greyman said:


> It wasn't, and the first ones to tell you that would be the British Air Ministry. They chose the .303 Browning to replace the Vickers Mk.V in 1934. By 1937 they had already decided that the 20mm Hispano should replace it. But, you can't just snap your fingers and change something like that. Reality got in the way - right up until 1945.



Quite right, and the reason they went with the Browning instead of keeping the Vickers was the the Vickers had a rather alarming tendency to jam. The Jams could often be cleared _fairly_ easily but required some sort of access to the gun. in WW I and shortly thereafter the RAF had used Lewis guns in wing (or underwing) mounts because of the reliability issue. This rather rules out adopting the .5 Vickers gun _as is_ at it would have the same jamming problem. 



Greyman said:


> It was possible, but the British didn't want it, for reasons already mentioned. They _were_ clamouring for more Hispano guns, which the US was trying to produce, but when the requirement for Spitfire guns was halved (the decision being made to only equip them with two cannon) the British could rely on their own production.



to add to that, the British _had_ tested the .50 cal Browning back in the trials that lead to the adoption of the small Browning. But the .50 cal Browning of the late 20s and early 30s was NOT the .50 cal Browning of 1942/43. It used ammo that was several hundred fps lower in velocity and had a max cycle rate of under 600rpm. This is for a gun in a test stand with a "short" belt of ammo. Trying to pull a long belt slowed the gun down. When synchronized to fire through the propeller the cycle rate fell to under 500rpm and in some cases was closer to 400 rpm on some of the P-40s the British first got. The M2 Ball ammo ( and other loads/types to correspond) don't show up until the mid/late 30s. The US does not improve the rate of fire until some point in 1940. Before or after the BoB I don't know. 
I don't have the production figures at hand and so may be wrong but if .50 cal production followed most of the rest of US production you had a trickle in 1940/41, a fair number in 1942, a river in 1943 and an avalanche in 1944 and were trying to figure out how to stop it in 1945. 
Just found some figures, Production of ALL types of .50 cal machine guns from July 1 1940 on. 1940-5155 guns, 1941-49,479 guns, 1942- 347,492 guns, 1943-641,638 guns, 1944-677,011 guns, 1945-239,821 guns. 
It would not be until some point in 1943 that the US would be in a position to supply any real quantity of guns on a steady basis even with very careful accounting and not stockpiling guns for future needs. ( how many air frame programs were running behind schedule or other needs that fluctuate). 




Greyman said:


> The idea was '_is it wise to put all the eggs in one basket?_' If you miss (which most pilots did) you miss with all. It wasn't necessarily 'the British idea' either. Most Air Forces spread their guns somewhat.



Against a small fighter fuselage a lot of these patterns might leave something to be desired. Against something like a He 111 as long as the pilot did his job ( the biggest IF in the question) some of the patterns offered a 50-75% hit rate out to 400 yds from a 6 oclock ( 0 deflection) aiming point. Spitfire patterns changed a number of times during the war and went from ( apparently) all guns in line converging at different distances, starting at 350 yds or more and changing to 250 yds (or less?) with the eight machine guns to some rather complicated patterns with the 20mm guns forming a figure 8 at the cross over distance and the 4 MGs aligned (or mis aligned ) to hit at different heights and horizontal distances at _ALL_ ranges. 

In favor of the wide spread for bomber interception was the fact that actual kills were NOT the objective. Stopping the bomber before it reached it target was. If you can damage the bomber and force it to turn back/jettison it's load you have succeeded in defending the target. Granted a damaged bomber bomber can be repaired and fly other missions but on any given day/night the more bombers the fighters can put bullets into the greater number they _may_ stop even if the total kills for that day are bit lower than more concentrated fire. 

Some "spreads" are pretty nominal. 

Convergence diagram for a P-47;







Notice that even if the inner guns were set for 250 yds and the outer ones for 350 yds it is possible to have ALL guns hitting in a area about 12 feet wide from 100 yds to 400 yds range. With guns starting at around 18-20 ft apart that doesn't seem too bad.


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## Shortround6 (Jul 24, 2013)

pinsog said:


> The idea was '_is it wise to put all the eggs in one basket?_' If you miss (which most pilots did) you miss with all. It wasn't necessarily 'the British idea' either. Most Air Forces spread their guns somewhat.



But that doesn't make sense. A few random bullets from one rifle caliber machine gun is unlikely to bring down an HE111, DO17 or JU88. I understand that many British pilots during the BoB were not well trained, especially in gunnery and that they had to get REALLY close to hit anything. But again, pointing all of your guns in different directions will not give you enough damage for a kill. What is the point of aiming each gun in a different direction just to be able to claim you hit an aircraft? "Hey guys, I put 20 bullets into a German bomber today. It will take them at least 10 minutes to patch that up when they get back" If you are going to shoot at enemy bombers, your goal should be to destroy them, not hit them randomly with a dozen or so bullets while your other guns are blazing away off in a different direction. Also, if you are going to close to less than 50 yards on an enemy bomber, which untrained British pilots often did, you should be able to hit it with your guns concentrated in a small target area.[/QUOTE]

If they got within 50yd the guns would mostly all hit, the guns were NOT pointed THAT badly. 

According to the diagram for Spitfire Bullet pattern 1, from the 6 O'clock postition, the out board guns would hit a He 111 just out board of the engine nacelles, the middle pair would hit just inboard of the engine nacelles with an over lapping pattern and the inner guns hitting just outboard of the wing root fairing. the 75% zone for each gun was about the thickness of the He 111s wing in diameter. as the range gets longer the 75% zones get bigger but they move in closer to the fuselage and blend together more until at 300 yds ( with a 350 yd convergence) they look like a side ways figure 8 that has been traced over several times and overlaps a bit. The 75% zone from each and _every_ gun looks to be about 80-90% on the He 111 fuselage, at 400 yds the guns have crossed over and the 75% zone has grown greater than the diameter of the He 111 fuselage. 

The Diagram can be found on page 93 of Tony Williams and Emmanual Gustin's book "flying Guns World War II. 

Some British pilots, even with some training were opening fire on target sleeves at up to 1000 yds even when instructed to open fire at 300 yds.


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## Greyman (Jul 24, 2013)

pinsog said:


> But that doesn't make sense. A few random bullets from one rifle caliber machine gun is unlikely to bring down an HE111, DO17 or JU88. I understand that many British pilots during the BoB were not well trained, especially in gunnery and that they had to get REALLY close to hit anything. But again, pointing all of your guns in different directions will not give you enough damage for a kill. What is the point of aiming each gun in a different direction just to be able to claim you hit an aircraft? "Hey guys, I put 20 bullets into a German bomber today. It will take them at least 10 minutes to patch that up when they get back" If you are going to shoot at enemy bombers, your goal should be to destroy them, not hit them randomly with a dozen or so bullets while your other guns are blazing away off in a different direction. Also, if you are going to close to less than 50 yards on an enemy bomber, which untrained British pilots often did, you should be able to hit it with your guns concentrated in a small target area.



To illustrate the point, I'll take things to a ridiculous extreme ...

Imagine if the Spitfire I was armed with eight 30mm ADEN guns. Would you not agree that harmonising them to a single point would be a waste? Would it not be better to create a pattern that conforms to the shape on an enemy aircraft from 200 yards to 400 yards? Instead of just a single point at 250 yards. 

The disconnect here is what constitutes 'lethal density'. The British (AFDE specifically) had their data from before the war, and that's what they went on. 

How armoured were German pilots, coolant and oil systems in 1939?
What was the average aiming error of British pilots from gun camera exercises?
How effective is massed fire from German bomber formations? Is closing to 50 yards before firing a good thing to do?


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## Greyman (Jul 24, 2013)

Shortround6 said:


> Spitfire patterns changed a number of times during the war and went from ( apparently) all guns in line converging at different distances, starting at 350 yds or more and changing to 250 yds (or less?) with the eight machine guns to some rather complicated patterns with the 20mm guns forming a figure 8 at the cross over distance and the 4 MGs aligned (or mis aligned ) to hit at different heights and horizontal distances at _ALL_ ranges.



Basically it went like this:

*Sep 1938 -* harmonised to a point 350 yards ahead --- 'concentrated pattern'
*c.Sep 1939 -* harmonised to a large box pattern 400 yards ahead --- 'horizontal harmonization' (British Forces in France continued to harmonise to a point 350 to 150 yards ahead, depending on Squadron)
*c.Dec 1939 -* two squadrons switch to a large circular pattern 200 and 400 yards ahead --- 'circular harmonization'
*Jan 1940 -* ten squadrons switch to concentrated pattern
*Feb 1940 -* full RAF switch to concentrated pattern
*c.mid 1942 -* 'spread pattern' (which you somewhat described)


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## Shortround6 (Jul 25, 2013)

Thank you, the "Spread pattern" is shown somewhere in the book I mentioned earlier but it it is a real pain to describe in text. 

I too will carry something to a ridiculous extreme to agree with you.

Barrage balloons and smoke generators brought down very few bombers but were an important part of air defense because they lowered the effectiveness of the enemy bombers. They forced them to fly higher or helped hide the targets from the bomb aimers.
Likewise early AA guns scored few kills but often made bomber crews drop early/late/wide or pick another target.

Many times a weapon's/tactic's effectiveness cannot be measured by simple kill/loss ratios.


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## Greyman (Jul 25, 2013)

One of the very reasons to continue to carry .303-inch guns: it forces your enemy to armour against .303-inch guns. It's pointless to try and armour against Hispano 20-mm rounds, but if you're carrying .303 Brownings - now your enemy has to carry hundreds of extra pounds in armour.


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## pinsog (Jul 25, 2013)

.


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## pinsog (Jul 25, 2013)

Greyman said:


> To illustrate the point, I'll take things to a ridiculous extreme ...
> 
> Imagine if the Spitfire I was armed with eight 30mm ADEN guns. Would you not agree that harmonising them to a single point would be a waste? Would it not be better to create a pattern that conforms to the shape on an enemy aircraft from 200 yards to 400 yards? Instead of just a single point at 250 yards.
> 
> ...



Your extreme example doesn't make sense. A single 30mm ADEN cannon could easily bring down any aircraft in WW2, perhaps finding the B29 a bit more difficult. The 303 (or any 30 caliber or 8mm rifle cartridge) is terribly underpowered for shooting down aircraft in WW2 (possibly excepting the early war biplanes and other obsolete aircraft). Rifle caliber machine guns must be concentrated to be effective on the aircraft the Germans were using because the individual cartridge was weak. Just like ants, an individual ant attacking a scorpion or large spider is not going to fair well, a swarm of them can kill about anything. If you are forced to hunt crows or ducks with #9 birdshot, you better use a full choke so you hit your target with a good chunk of the pattern. If you use #9 birdshot with a cylinder bore on a crow, about all you are going to do is make noise, you probably wont even knock any feathers off, much less bring down the target. 

If they stuck me in a Spit or Hurricane during the BoB, I would tell them to put all 8 guns in as small a box as possible at 100 yards.


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## CobberKane (Jul 25, 2013)

Greyman said:


> One of the very reasons to continue to carry .303-inch guns: it forces your enemy to armour against .303-inch guns. It's pointless to try and armour against Hispano 20-mm rounds, but if you're carrying .303 Brownings - now your enemy has to carry hundreds of extra pounds in armour.



That's one of the more interesting pieces of logic I've heard in a while. For starters armour could and did frequently stop 20mm rounds during WWII. Enemy fire was as likely as not to strike at an angle, where all or much of the energy could be negated by armour plate. Also, armour wasn't just installed to counter airborne LMGs; it was also there to provide protection from shrapnel and bullets from all calibres of ground fire.
By your reasoning, had allied aircraft been armed exclusively with cannon by 1944, the Germans would have responded by stripping all the armour from their fighters. A little counter-intuitive, to put it mildly


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## Shortround6 (Jul 25, 2013)

pinsog said:


> If they stuck me in a Spit or Hurricane during the BoB, I would tell them to put all 8 guns in as small a box as possible at 100 yards.



That rather limits your options as at 200yds the guns would as spread out as they are in the plane. Roughly for a Spitfire about 7 ft from the center line, then just under 9ft , just over 9 ft and about 12 ft. With a 200yd cross at 100 yds the guns are hitting at half their actual installed distances. Please note that on a P-47 the closest guns are about 9 ft from the center line. 

With a 200 yd cross ALL guns would be hitting in an area about 6 feet wide anywhere from 150-250 yds range. with a 250 yd cross the sweet spot is a little further away but is also a bit longer.

Your 100 yd cross means your outer guns are 24ft apart at 200 yds and your 4 "middle" guns are about 18ft apart at 200yds. At 300yds you have bullets all over the sky, your outer guns are now hitting 48 ft apart and the "middle guns" are 36ft apart, even the inner guns are about 28 ft apart. 

You HAVE to get close to 100yds to have an effective pattern. Forcing ALL your pilots to close to 150 yds and under is going to increase losses from collisions and hitting debris.


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## pinsog (Jul 25, 2013)

Shortround6 said:


> That rather limits your options as at 200yds the guns would as spread out as they are in the plane. Roughly for a Spitfire about 7 ft from the center line, then just under 9ft , just over 9 ft and about 12 ft. With a 200yd cross at 100 yds the guns are hitting at half their actual installed distances. Please note that on a P-47 the closest guns are about 9 ft from the center line.
> 
> With a 200 yd cross ALL guns would be hitting in an area about 6 feet wide anywhere from 150-250 yds range. with a 250 yd cross the sweet spot is a little further away but is also a bit longer.
> 
> ...


 
You might bump it out to 150 yards, but I wouldn't want it to be any further than that due to the poor hitting power of the 303. One of the reasons given for using the high rate of fire 303's in place of the Browning 50 during the BoB, is that the relatively untrained British pilots could shoot worth a crap so they would just spray random fire at German bombers hoping to hit them. If that was indeed the case, then 100 to 150 yards is probably farther than they could hit anything anyway. Now a P47 would be a different deal. The 50's could be set much farther out since they have so much more power.


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## Shortround6 (Jul 25, 2013)

I think you have a rather poor opinion of of the .303 ammo, which seemed to work just fine for the Japanese in a number of their aircraft guns in Dec 1941 and a good part of 1942. 

.303 ammo doesn't turn into spitballs at 200yds. It may have been far from ideal but it did manage to shoot down several thousand Axis aircraft. 

And effective range would vary with altitude. 

A major problem is range estimation and leading (deflection shooting). Time of flight becomes rather important. 

The 250 yard cross is going to give around 110-120 bullets into about a 6ft wide by 2 ft high area in one second for a bit if a distance on either side of the actual cross point. If this isn't concentrated enough what is? (and that is allowing for a 75% hit zone, a 1005 hit zone might be 8-9 feet wide and 3-4 feet high and up the hits to 150-160 in one second). Shortening the effective range of the fighter to 150 yds or less is not the answer. It will be much harder to get into effective firing positions. it make s range estimation much more critical ( if a pilot you thought he was a 300 yds was actually at 800-1200yds what happens to your 100 yd convergence if if he _thinks_ he is at 100 but is actually at 300yds? see above spreads in previous post. 

The high rate of fire .303 in the BoB was really high because the .50 cal Browning was lucky it could reach 600rpm synchronized at the time. Throw that in with the weight of .50 cal guns and ammo and it was no contest. for the weight of eight .303 Brownings and 350 rounds per gun you could get _four_ .50 cal guns and 75-80 rounds per gun. 8 seconds of firing time at 40 rounds per second vs 17 seconds firing time at 150-160 rounds per second. Merlin III was good for 880 hp for take-off unless you used emergency boost.


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## Greyman (Jul 26, 2013)

pinsog said:


> Your extreme example doesn't make sense. A single 30mm ADEN cannon could easily bring down any aircraft in WW2 ... The 303 (or any 30 caliber or 8mm rifle cartridge) is terribly underpowered for shooting down aircraft in WW2 (possibly excepting the early war biplanes and other obsolete aircraft).



I'm not sure how else to get my point across, sorry. All I can say is that the British believed the .303 Browning to be more effective than you do.



CobberKane said:


> That's one of the more interesting pieces of logic I've heard in a while. For starters armour could and did frequently stop 20mm rounds during WWII. Enemy fire was as likely as not to strike at an angle, where all or much of the energy could be negated by armour plate. Also, armour wasn't just installed to counter airborne LMGs; it was also there to provide protection from shrapnel and bullets from all calibres of ground fire.
> By your reasoning, had allied aircraft been armed exclusively with cannon by 1944, the Germans would have responded by stripping all the armour from their fighters. A little counter-intuitive, to put it mildly



I understand what you're saying, and it _is_ more complicated than that, and isn't my reasoning, but - I can't find the document where this thought is mused (among a mass of RAF/Air Ministry/etc. correspondence of how to deal with this new Fw 190). 

I meant it more as a small quip to toss onto Shortround's pile and not an Official Ministry of the Air Reason 4.a) on why .303-inch calibre was used.



pinsog said:


> You might bump it out to 150 yards, but I wouldn't want it to be any further than that due to the poor hitting power of the 303. One of the reasons given for using the high rate of fire 303's in place of the Browning 50 during the BoB, is that the relatively untrained British pilots could shoot worth a crap so they would just spray random fire at German bombers hoping to hit them. If that was indeed the case, then 100 to 150 yards is probably farther than they could hit anything anyway. Now a P47 would be a different deal. The 50's could be set much farther out since they have so much more power.



Hitting power of .303 rounds wont be much effected by an extra hundred or so yards. Accuracy will, hence the spread patterns.


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## CobberKane (Jul 26, 2013)

Greyman said:


> I'm not sure how else to get my point across, sorry. All I can say is that the British believed the .303 Browning to be more effective than you do.
> 
> 
> 
> It would seem so, wouldn't it? At least when combined with cannon. It was mentioned earlier that the .303s would give the Spit, Mossie etc at least some capability after the Cannons ran out of ammo. I can see that being true with regards to the Spit V with its drum fed Hispanos, but later Spits had belt fed cannon and twice the ammo load - and they could have carried more again if the Brits had considered it worthwhile making room by ditching the LMGs. Standardisation of calibre with small arms also seems logical, but the Aussies used Lee-Enfields and Brens too, yet they still chose to put HMGs on their Beaufighters. Maybe it was a case of, if it ain't broke don't fix it, like the USAAF sticking with the .50 because going with cannon would have been a major hassle for extra firepower that wasn't really needed anyway.


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## fastmongrel (Jul 26, 2013)

Never understood why Mossies and Beaus carried MGs I mean if you cant knock down a plane with 4 x 20mm Hispanos, then 4 or 6 .303s arent going to do it.


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## Shortround6 (Jul 26, 2013)

CobberKane said:


> Greyman said:
> 
> 
> > Standardisation of calibre with small arms also seems logical, but the Aussies used Lee-Enfields and Brens too, yet they still chose to put HMGs on their Beaufighters. Maybe it was a case of, if it ain't broke don't fix it, like the USAAF sticking with the .50 because going with cannon would have been a major hassle for extra firepower that wasn't really needed anyway.
> ...


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## swampyankee (Jul 26, 2013)

CobberKane said:


> This one has doubtless come up before, but what the hell. By the end of the BoB it was - from all accounts - pretty obvious that the Browning .303 lacked the firepower to reliably deal with increasingly tough LW fighters and bombers. The Hispano 20mm proved the answer. Yet the Browning persisted in conjunction with the larger gun on Spitfires, Mosquitos and Beaufighters. Why? Wouldn't ditching the Browning for half as many .50s or a couple of extra cannon have made sense? Or was there something about the way lots of small projectiles complemented the explosive cannon shells that that made the combination more than the sum of it's parts?



The USAAF and USAF persisted with 0.5 in MG for several years after every other service had decided it lacked the firepower to deal with modern aircraft; the RAF probably kept the 0.303 in for the same reason: inertia. For the turreted installations, it was probably lack of an acceptable alternative and perceived lack of effectiveness of bomber defensive armament, especially at night without any sort of radar assistance.


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## Edgar Brooks (Jul 26, 2013)

It really is astounding the strange stuff, at times, which is written on this subject (how, on earth, could you fit the non-existent Aden 30mm into a Spitfire wing?); the RAF did not go for a spread pattern, in fact I have a copy of the harmonisation diagram, for the Vc (which would also have held good for the VII, VIII, IXc, and XIVc until war's end,) which was to be set up at a range of 50 yards, and concentrated the aim of all guns, camera, and gunsight at 250 yards.
The Air Ministry (not the RAF) stayed with the battery of 4 x .303" (in the teeth of opposition by Leigh-Mallory) because it was felt that, in a deflection shot (at which, in general, pilots were not very good,) the four guns had a better chance of disabling the enemy pilot, who had little, or no armour at his side, than two slower-firing .5". It had also been found that the .5" was no better at penetration of German armour, in astern shots, which didn't help. And, I'm sorry, Pinsog, but RAF pilots were not "relatively untrained"; "aiming-off" "deflection shooting" call it what you will, takes a certain skill, which not everyone can master, and the likes of Tuck, Johnson, Bader, etc., used to go duck-shooting to hone their skills, something that was not always available to the ordinary pilot.
When the gyro gunsight appeared in 1944, it changed things completely, since it virtually guaranteed that pilots would hit what they were aiming at, and that was when the Air Ministry finally allowed usage of the .5".


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## Timppa (Jul 26, 2013)

CobberKane said:


> By your reasoning, had allied aircraft been armed exclusively with cannon by 1944, the Germans would have responded by stripping all the armour from their fighters. A little counter-intuitive, to put it mildly



I agree that the reasoning is weird, but that was just what Finnish Air Staff ( who were pretty inept people, IMO) did.
In 1943 they learned that the seat armor of the Curtiss fighters were inadequate stop 7.7mm AP round from close range.
Solution: Order to remove the seat armor.


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## pinsog (Jul 26, 2013)

And, I'm sorry, Pinsog, but RAF pilots were not "relatively untrained"; "aiming-off" "deflection shooting" call it what you will, takes a certain skill, which not everyone can master, and the likes of Tuck, Johnson, Bader, etc., used to go duck-shooting to hone their skills, something that was not always available to the ordinary pilot.[/QUOTE]

I have never read anything about how well British pilots were trained until coming to this forum. My information came from several other discussions on the BoB and various armament discussions right here on this forum, where several well informed people (they seemed well informed to me at the time) stated that many British pilots at the time of the BoB were relatively untrained, especially in the area of air to air gunnery skills, having little to no training at all before being thrown into combat. The reason stated was that the RAF had already lost many of her trained professional pilots over France and they were being replaced with men whe they hadnt had time to properly train. Later on the training caught up and they were among the best in the world. This was given as one of the many reasons they stuck with the 303 over other slower firing but more powerful weapons and to make up for the lack of power of the 303 and the lack of gunnery training of the pilots, they got in REALLY close to the bombers. I only recently read that they didnt concentrate all of there weapons into a small area, which was a huge suprise to me. I would have thought concentrating them would be common sense.

Seemed reasonable to me and after reading several posts in different places stating that many BoB British pilots were lacking in skills, I came to take it as fact. I'm not bashing British pilots, merely passing on what I have read in this forum. Everyone in WW2 had periods where they were putting pilots in combat that weren't ready.


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## stona (Jul 26, 2013)

Edgar Brooks said:


> The Air Ministry (not the RAF) stayed with the battery of 4 x .303" (in the teeth of opposition by Leigh-Mallory) because it was felt that, in a deflection shot (at which, in general, pilots were not very good,) the four guns had a better chance of disabling the enemy pilot, who had little, or no armour at his side, than two slower-firing .5". It had also been found that the .5" was no better at penetration of German armour, in astern shots, which didn't help. And, I'm sorry, Pinsog, but RAF pilots were not "relatively untrained"; "aiming-off" "deflection shooting" call it what you will, takes a certain skill, which not everyone can master, and the likes of Tuck, Johnson, Bader, etc., used to go duck-shooting to hone their skills, something that was not always available to the ordinary pilot.



This is true. There is a difference between being "untrained" and being a bad shot!
Air to air gunnery at the sort of speeds aircraft were flying at by the late 1930s using unsophisticated gun sights (iron rings in some cases) was a difficult art to master. The RAF discovered from early gun camera footage that its pilots were not at all good at estimating range, let alone "angle off". Even firing with little or no deflection (the system that Bader incidentally considered the best, whether he went duck hunting or not) is fairly pointless with machine guns at a range of 1500 yards which was the range that some BoB era pilots were shown to be shooting from.
Cheers
Steve


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## pattle (Jul 26, 2013)

Pinsong, I don't know exactly why the RAF continued using the Browning 303 for so long other than that it still must have been useful. I assume that more and more of the RAF's fighter ammunition was expended against ground targets rather than against air targets as the war progressed. You are right a lot of the Battle of Britain pilots were very inexperienced for the reasons you gave.


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## Dogwalker (Jul 26, 2013)

When the armament of the aircrafts that participated to BoB was decided, however, RAF can't predict to have to rely on a mass of relatively trained/untrained pilots, and when BoB was over, RAF had no more to rely on pilot with litte training, so, as a reason, it doesn't seems so good.


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## Greyman (Jul 26, 2013)

Edgar Brooks said:


> It really is astounding the strange stuff, at times, which is written on this subject (how, on earth, could you fit the non-existent Aden 30mm into a Spitfire wing?)


You absolutely couldn't. Don't worry about it.



Edgar Brooks said:


> the RAF did not go for a spread pattern, in fact I have a copy of the harmonisation diagram, for the Vc (which would also have held good for the VII, VIII, IXc, and XIVc until war's end,) which was to be set up at a range of 50 yards, and concentrated the aim of all guns, camera, and gunsight at 250 yards


The RAF changed policy on their harmonisation process several times throughout the war. From early 1940 until mid 1942 the RAF standardized on the 'concentrated pattern'. After which they switched to the 'spread pattern'. As far as I can tell this was used until the end of the war.



Edgar Brooks said:


> When the gyro gunsight appeared in 1944, it changed things completely, since it virtually guaranteed that pilots would hit what they were aiming at, and that was when the Air Ministry finally allowed usage of the .5".


I think there is a lot to this. Although I don't have a specific source for it - reading through Mk.IId Gyro Gunsight manuals indicates that the sight was, of course, calibrated for 20-mm Hispano fire. The .5-inch Browning round roughly corresponds to the same trajectory at the ranges required, whereas the .303-inch Browning is way off. The method for using the Mk.IId sight with .303 Brownings only is very awkward and the whole process is greatly simplified by using the .5-inch Browning as the secondary weapon.


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## Shortround6 (Jul 26, 2013)

pinsog said:


> I only recently read that they didnt concentrate all of there weapons into a small area, which was a huge suprise to me. I would have thought concentrating them would be common sense.



Define "small area"?
The standard pattern for a Spitfire had all eight guns hitting an area (or two areas) going from about 1/2 way between the engine and fuselage on one side of an HE 111 at 200 yds to the same point on the other side with a gap in the middle so each "group" much pretty much centered on the wing root. at 300yds they had sort of an overlapped sideways figure 8 only a couple of feet wider than the He 111 fuselage. At 350 yds (the cross over point) all eight guns would have a 75% circle all centered on the He 111 fuselage and no bigger than the fuselage diameter. As has been said, during the BoB the cross over was shifted to 250yds and the 75% circle would have been correspondingly smaller. 

How much smaller do you want the pattern to be?


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## pinsog (Jul 26, 2013)

pattle said:


> Pinsong, I don't know exactly why the RAF continued using the Browning 303 for so long other than that it still must have been useful. I assume that more and more of the RAF's fighter ammunition was expended against ground targets rather than against air targets as the war progressed. You are right a lot of the Battle of Britain pilots were very inexperienced for the reasons you gave.



Same reason we went to war with P39, P40, Brewster Buffalo fighters and Devastator torpedo planes, as Donald Rumsfeld so eloquently put it "you don't go to war with what you want, you go to war with what you have at the time" 

The British had no Browning 50's on hand, nor 20mm cannon. What they had was a bunch of Browning 303's and enough ammo to supply them, so that is what they used.


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## pinsog (Jul 26, 2013)

Shortround6 said:


> Define "small area"?
> The standard pattern for a Spitfire had all eight guns hitting an area (or two areas) going from about 1/2 way between the engine and fuselage on one side of an HE 111 at 200 yds to the same point on the other side with a gap in the middle so each "group" much pretty much centered on the wing root. at 300yds they had sort of an overlapped sideways figure 8 only a couple of feet wider than the He 111 fuselage. At 350 yds (the cross over point) all eight guns would have a 75% circle all centered on the He 111 fuselage and no bigger than the fuselage diameter. As has been said, during the BoB the cross over was shifted to 250yds and the 75% circle would have been correspondingly smaller.
> 
> How much smaller do you want the pattern to be?



I would want all 8 guns impacting at the same point, 150 to 200 yards(not sure how small a point 8 guns can be focused on). Personal preference, other people might want them spraying all over the place. When I bird hunt, with the exception of quail, I always use a full choke on a shotgun. I don't like to lightly spray a bird and hope it brings it down, I like to hit him with everything I have or miss him clean. Again, just my personal choice, most of my friends use a more open choke than I do on a shotgun, so pilots of the time might want a more open pattern, some might like the tight pattern, others might just use whatever is handed to them and not care.


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## Shortround6 (Jul 26, 2013)

If your target is a bomber and ALL your guns will put ALL the bullets they can ( there seems to a dispersion problem with getting a 100% zone from each gun to to be under several feet at several hundred yds) into an area smaller than the bombers fuselage diameter at 300yds good does going tighter do? That is hardly spraying all over the place like some of the earlier patterns. And if you set the cross point too close you will be spraying all over the place if forced to take a long shot (long being 300-400yds)

from another diagram to show British pilots proper aiming points, if a He 111 is doing 250hp and the fighter is just 7 degrees off the tail at 250yds the proper aiming point is just outboard of the 'inside' engine and level with the fuselage. If the pilot aims at the fuselage his bullets will go just under or barely hit the bottom of the outboard engine nacelle with a 1/3 degree dispersion pattern. If the guns have a 1 degree dispersion pattern there will be at least some hits along the wing, outside horizontal stabilzer/elevator and engine nacelle. at 400 yds and a 11 1/4 degree angle the proper aim point is over the inside wing tip. 

By the way a full choke puts 70% of it's pellets in a 30in circle at 40 yds or about 1.25 degrees. a 1.25 degree pattern at 300yds is about 19ft.


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## Edgar Brooks (Jul 26, 2013)

Greyman said:


> The RAF changed policy on their harmonisation process several times throughout the war. From early 1940 until mid 1942 the RAF standardized on the 'concentrated pattern'. After which they switched to the 'spread pattern'. As far as I can tell this was used until the end of the war.


The information we have is the other way round; the "Dowding spread" was his original approved method for attacking bombers (which were all that were expected before France fell,) but pilots didn't like it, and swiftly changed over when they encountered small fighters.


> I think there is a lot to this. Although I don't have a specific source for it - reading through Mk.IId Gyro Gunsight manuals indicates that the sight was, of course, calibrated for 20-mm Hispano fire. The .5-inch Browning round roughly corresponds to the same trajectory at the ranges required, whereas the .303-inch Browning is way off. The method for using the Mk.IId sight with .303 Brownings only is very awkward and the whole process is greatly simplified by using the .5-inch Browning as the secondary weapon.


At 250 yards, there was little difference in the trajectory of the three different rounds (if there had been, the Air Ministry couldn't have justified sticking with the .303".) Also, the harmonisation chart set the angles of all of the guns so that they met at 250 yards, which negates any differences (if the pilot gets his range right.)
Sorry, Pinsog, but you didn't make it plain that your "untrained" remark concerned only the Battle of Britain (which is true); I was referring to the whole spread of the war.
The problem with your shotgun analogy is that you (presumably) fire from a standing position; try it while running at full pelt alongside the bird, and see the difficulty of aircraft pilots who had to aim a moving object at another moving object, while allowing for "angle-off."


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## Greyman (Jul 26, 2013)

Edgar Brooks said:


> The information we have is the other way round; the "Dowding spread" was his original approved method for attacking bombers (which were all that were expected before France fell,) but pilots didn't like it, and swiftly changed over when they encountered small fighters.


Basically correct, but the reason was the inverse. According to representatives of the BAFF (Wing Commander C. Walter), their pilots were supportive of a slightly spread-out pattern in fighter vs. fighter combats - but for destroying bombers the highest density possible was preferred.

Now, don't confuse the Horizontal Pattern ('Dowding Spread') with the Spread Pattern. The latter was different pattern and adopted mid 1942, replacing the Concentrated Pattern ('Point Harmonisation').



Edgar Brooks said:


> At 250 yards, there was little difference in the trajectory of the three different rounds (if there had been, the Air Ministry couldn't have justified sticking with the .303".) Also, the harmonisation chart set the angles of all of the guns so that they met at 250 yards, which negates any differences (if the pilot gets his range right.)



Trajectory wouldn't be the problem, time of flight would.
EDIT: Also, that's the beauty of that Gyro Gunsight. Those 400-600 yard shots that were pointless with the standard gunsight are now possible. And at those ranges the 250 yard harmonisation of .303 and 20mm guns are quite a ways off.


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## Edgar Brooks (Jul 27, 2013)

Can you tell me where the references to Spread Pattern come from, please? In 30 years of looking through records, I've never seen mention of it, and what's the BAFF?


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## Greyman (Jul 27, 2013)

Edgar Brooks said:


> Can you tell me where the references to Spread Pattern come from, please? In 30 years of looking through records, I've never seen mention of it, and what's the BAFF?



Shortround referenced the Spread Pattern here: Flying Guns World War II


Shortround6 said:


> The Diagram can be found on page 93 of Tony Williams and Emmanual Gustin's book "flying Guns World War II.



My own references come from documents from the London PRO. I've been writing an article up on RAF WWII harmonisation patterns for a long time now, someday I'll light a fire under it and get it done - hopefully.

BAFF: British Air Forces in France - Wikipedia, the free encyclopedia


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## Dogwalker (Aug 1, 2013)

Curiously, having to face the same enemy, the Soviets came to opposite conclusions than the British, and decided then, at least for cowling mountings, a single heavy MG was better than two light MGs for about the same weight. Both the Yak-1 than the MIG-3 had two 7.62 mm ShKAS MGs replaced with one 12.7 mm UBS (so the first having one UBS and one cannon, the second two UBS) after the first months of war.


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## swampyankee (Aug 2, 2013)

Dogwalker said:


> Curiously, having to face the same enemy, the Soviets came to opposite conclusions than the British, and decided then, at least for cowling mountings, a single heavy MG was better than two light MGs for about the same weight. Both the Yak-1 than the MIG-3 had two 7.62 mm ShKAS MGs replaced with one 12.7 mm UBS (so the first having one UBS and one cannon, the second two UBS) after the first months of war.



The US M2 0.5 in had a performance superior to the British 0.5 in Vickers and inferior to the Soviet 12.7 mm UB and UBS.


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## Shortround6 (Aug 2, 2013)

Sometimes there are other considerations, from Wiki so take it for what you think it is worth;

"" The ShKAS machine gun had a high rate of fire but it also had 48 ways of jamming. Some of them could be fixed immediately, some could not. And 1,800 rounds a minute was an insanely high rate of fire. If you pulled the trigger too long, the ShKAS would fire all its ammo in one go and that would be it!!"

The last may be more for flexible guns than fixed. and

"The Shkas was a comparatively intricate and well finished gun, the cost of which necessitated that it be kept in operating condition as long as possible by repair and replacement of parts. In contrast to the Shkas, the Beresin was deliberately expendable, that is, the Soviets' plan was to discard the entire gun after a short period of use during which one or another of the principal operating mechanisms became worn or broken."

If the 12.7 mm UB offered even close to the same target effect as a pair of ShKAS and was cheaper to produce (money, man ours, what ever) and posed less of a maintenance burden it would be picked even in not actually "better". 

I don't know how much each different consideration counted but many times a weapon was kept in production/use or dropped for other reasons than target effect alone.


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## stona (Aug 2, 2013)

The sights......the sights 







Steve


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## Dogwalker (Aug 2, 2013)

Of the Shkas there was even a 3000 RPM version (that really unreliable), the normal Shkas fired at 1800 RPM, and about 1650 when synchronized, so about 50% more than a Browning 303. But, for a comparison of weapons designed in the same years, the MG-81 fired 1600 RPM without being a revolver. As for the ammo load, a Mig-3 had 750 round per weapon, so 27 second of fire, Less than a Bf109f, but much more than a early Spit. 
For jamming consideration, it's strange to replace two Mgs with one, especially if, if one of the two Shkas is jammed, the remainant could fire two rounds for every round fired by the UBS (800 RPM).
From wiki also, it seems Soviets were unimpressed by the reliability of the Browning 303: _The .303 variant equipped the Hawker Hurricanes delivered to Soviet Air Forces, during the Great Patriotic War. Soviet airmen compared them to Soviet ShKAS in terms of reliability: "But they often failed due to dust," recalled pilot Nikolai G. Golodnikov. "We tackled the problem gluing percale on all the machine-gun holes, and when you opened fire, bullets went right through. The machine guns became reliable then. They were of low efficiency when fired from distances of 150-300m"._


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## Edgar Brooks (May 25, 2014)

Dogwalker said:


> From wiki also, it seems Soviets were unimpressed by the reliability of the Browning 303: _The .303 variant equipped the Hawker Hurricanes delivered to Soviet Air Forces, during the Great Patriotic War. Soviet airmen compared them to Soviet ShKAS in terms of reliability: "But they often failed due to dust," recalled pilot Nikolai G. Golodnikov. "We tackled the problem gluing percale on all the machine-gun holes, and when you opened fire, bullets went right through. The machine guns became reliable then. They were of low efficiency when fired from distances of 150-300m"._


The Russians never were very good at listening to advice; the RAF had been covering the muzzles of their Brownings, first with metal covers, then doped fabric, since 1939, and that was due to the open breeches freezing at the usual fighting altitudes in the U.K., not dust.


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