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

[CobberKane]

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?

 

[Ivan1GFP]

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.

 

[beitou]

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?

 

[Jabberwocky]

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.

 

[stona]

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

 

[Shortround6]

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

 

[Shortround6]

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.

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.

 

[Greyman]

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.

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.

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.

 

[Shortround6]

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.

 

[pattle]

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

 

[Greyman]

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

 

[Shortround6]

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.

 

[RCAFson]

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".

 

[davebender]

I agree.

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

 

[CobberKane]

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.

 

[pinsog]

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.

 

[beitou]

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

 

[CobberKane]

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.

 

[swampyankee]

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.

 

[bobbysocks]

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.