Impact of fully adopted and reliable 20mm in BoB

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Admiral Beez

Major
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Oct 21, 2019
Toronto, Canada
How would the Battle of Britain have been impact had all the RAF's Spitfires and Hurricanes been armed with reliable 20mm cannons?

This would entail the Spitfire Mk.V's armament of 2x20mm cannons and four x.303 mgs for all the RAF's Spitfires in the BoB.

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And for the Hurricanes, it's four 20mm cannons of the Mk IIC. The ultimate bomber killer.

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Maybe for the Hurricane I only at first as it had thick wings. Also, 2 cannons plus 4 LMG, not 4 cannon as they only had 60 rounds in a drum so you need the LMG as a backup. Of course, it would be better if the Hurricane had the extra 4 LMG in the outer wings also.
 
The answer is very simple. A lot less German bombers would have made it home. for ease of sums let's say that the 303 had twice the ROF of the 20mm. Then those German bombers that made it home with 200 hits from the 303 would have been hit by 50 or 25 20mm shells depending on the number carried. No early medium bomber has any realistic chance of getting home after that level of damage.

Its a very simplistic way of describing it I know, but it you get the point
 
I think you'll find that a Dornier or Stuka would gets its tail sawn off by the concentrated bullets from a Hurricane Ia.
 
SaparotRob said:
Would .50 caliber guns have been a better compromise? I've read of .303 caliber mgs called "paint scratchers" or is that a Caidinism?
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No doubt at all that a sorted 0.5" would be a better weapon but in 1940 the 0.5" wasn't sorted. The USA was still fitting 0.3" guns to fighters long after 1940. The ammunition in .303s was improved particularly with incendiary rounds. The British had pretty much resolved to go for 20mm cannon the issue was getting them to work.
 
SaparotRob said:
How about that. The Browning(?) M-2 has an excellent reputation. The problem was getting them to work in a plane?
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When the British tested the 0.5 in Browning vs their Vickers 0.5 in machine gun, they found very little to chose between the two, and neither to be particularly superior to the 0.303 in. I know there are people who still think the M2 was the be-all and end-all of WW2 aircraft guns, but both the USN and the USAAF were looking for a better gun throughout the war; they just couldn't get the 20 mm Hispano to work properly, because of poorly thought out design changes made by the US Army's ordnance division. Post-war, the USN abandoned the 0.5 in pretty quickly; they USAF got rid of it when they found it ineffective in Korea.
 
Admiral Beez said:
Yes, were discussing the impact had those problems been sorted out earlier.
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No, we're talking about If the 20 mm guns had been sorted out earlier. No, they couldn't have been. Yes they could have been deployed. Yes in the Hurricane, but extra 4. 303 guns in the outer wings would be needed when they failed
 
Glider said:
Then those German bombers that made it home with 200 hits from the 303 would have been hit by 50 or 25 20mm shells depending on the number carried.
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That's the trouble with the Whirlwind and its four cannons. With only 60 rounds per gun, for a total of 240 rounds, each gun firing 600–700 rpm, you'd need burst control to avoid needlessly avoid depleting all your shells into that first bomber. We need earlier belt feed systems for the Hispano-Suiza.
 
I have frequently thought it would have been a good idea to try it with 12 group, but that is all hind sight.
 
pbehn said:
It is a different usage, theres been some excellent posts explaining the problems and solutions, Soldiers don't go up to 30,000ft and perform 7 G turns with their M2s.
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Add to that the problems of the guns jamming because they were frozen, the effects of G and cold on the ammunition causing the feed to fail etc etc etc.
Read William Bartsch's book Doomed at the start where he describes in some detail the number of P-40s in the Philippines in December 41 that had all or most guns fail when sent into combat. Other aircraft had the same problems.
 
That's what I was alluding to when I mentioned 30,000 ft and 7G turns. I havnt read that but some posters here I am sure have read it or similar, There were all sorts of problems which took some time to resolve, happily they were. As with all things it seems simple, when its explained in detail by someone who knows what they are talking about, all becomes clear.
 
I always thought the US .50 cal was a good gun, from essentially the start.

Back to cannons, how we're the Japanese 20 mm cannons for reliability? Their Type 99 cannon entered service in 1939. The Russians had their ShVAK 20 mm cannon for their aircraft in the 1930s.

The Brits (and French) used the Hispano-Suiza HS.404, while the Japanese and Germans used a a copy/development of the Oerlikon FF. Did Britain test or consider the Oerlikon?
 
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