Cannon versus Machine Guns?

[PatG]

Historian Mr Holland claims in his documentary on the BoB that the 20mm cannon was a major advantage to the Luftwaffe in both the Bf109E and Bf110C but I have my doubts as his views are often quite misleading and incorrect, so I would be interested to hear what other people think.

 

In a 'bounce' scenario I can see how the hitting power of an explosive 20mm round on an unsuspecting target could be lethal but in a dog-fight scenario with targets twisting and turning the lower rate of fire of the cannon would mean the chances of actually hitting something with them would be greatly reduced and that mg's would offer a better chance of at least putting a few holes in the enemy. All the more relevant when Goering demanded that the escorting Bf109E's stayed closer to the bombers so denying them the opportunity to exploit the 'bounce', and presumably why Galland rather tongue in check requested Spitfires to best fulfil this new remit.

 

Interestingly the US, with some minor exceptions, never used the 20mm cannon and preferred the 0.5 inch Browning instead to great effect. And in Tom Neil's autobiography 'Scramble' he recalls how the 12.7 mm (0.5 ich) guns from the Macchi 202 were able to penetrate the seat armour in Hurricanes over Malta whereas the 20mm explosive cannon rounds from Bf109E's had failed to do so during the BoB.

 

No right answer I know and I'm not a big fan of Mr Holland due to his many dubious assumptions and errors but I'd very much like to know what others think on the subject.

 

Kind Regards

Pat.

 

 

 

 

 

 

 

 

Edited April 1 by PatG
typo

[Mike]

If I wanted to take photos, the Canon would be best, but for shooting down aircraft, I'd recommend guns every time

[PatG]

Oops!

 

Apologies for the typo and boosting sales of camera equipment!

 

Pat.😁

[Mike]

2 minutes ago, PatG said:

Oops!

 

Apologies for the typo and boosting sales of camera equipment!

 

Pat.😁

Don't worry about it.  It caused a wry smile at this end, so it's all good.  You can go about your sensible thread now without me interfering

[PatG]

Mike,

 

That's great, thank you.

 

And apologies again for posting stuff in the wrong place.

 

Pat.

[Mike]

1 minute ago, PatG said:

And apologies again for posting stuff in the wrong place.

It's already forgotten.  No, really.  I can't remember a damn thing about it!

[Graham Boak]

The RAF were completely sold on the advantage of the 20mm cannon as opposed to putting a few holes in thin metal areas.  As indeed were the Luftwaffe, the L'Armee de L'Air. and the VVS, and when they could the Japanese.  What you are missing is the difference in effect between the comparatively light 0.303 round and the heavier 0.5in/12,7mm  round  The latter was capable of penetrating the limited armour, and/or damaging structural elements, carried on WW2 fighters whereas the smaller bullet wasn't.  The 0.5 was also effective at longer ranges.  The Italian 12.7 round was actually explosive, and was generally thought to be ineffective because of that.  The small amount of explosive carried would explode on contact with the skin rather than hitting hard.   If Allied pilot armour was being penetrated in the Desert war then it was probably fired by an MG151,

 

Of course, not all 20mm cannon had the same effectiveness.  The Hispano was very powerful and long-ranged, but the price for that was weight.  The MG FF in the Bf.109E was much lighter and hence with poorer performance, although later versions with the FFM round were better.  The MG151, and Russian cannon, were superior all round to the early Swiss/German gun.

 

The US obsession with the 0.5 was partly that the cannon was "not invented here" and early licence builds of Hispanos had proven troublesome. However they were slowly coming round with more and more types using cannon rather than machine guns,  Significant is that they were rarely required to fire at strong well-protected aircraft, being almost entirely deployed against fighters in Western-Europe and the light unprotected structures of Japanese types.

 

The point about a single central cannon is that it is much more accurate than wing-mounted guns and thus it is easier to hit your target.  That's why Moelders thought the early Bf.109F, with its initially 15mm MG151 cannon, was a better mount than the Emil with 2x20mm MGFF.  Despite what was thought at the time, there were no central cannon fitted to the Emil.  The Russians had a similar philosophy, many of their pilots preferring the slow-firing but harder-hitting 37mm of the Yak 9T over the 20mm cannon of earlier Yaks.

 

[stevehnz]

5 hours ago, PatG said:

And in Tom Neil's autobiography 'Scramble' he recalls how the 12.7 mm (0.5 ich) guns from the Macchi 202 were able to penetrate the seat armour in Hurricanes over Malta whereas the 20mm explosive cannon rounds from Bf109E's had failed to do so during the BoB.

Not wanting to pick a fight but to me a statement like this needs quite a bit of qualification before it can be taken as proof of the superiority of the .5 over a 20mm cannon. Was this a proven trend or an occasional or anecdotal incident. I suspect that Tom Neil's comment refers to possibly only an isolated instance or two & maybe were the reported cannon rounds being stopped by essentially the same armour during the BoB more as reported in intelligence reports after the heat of battle  than proven in fact. It would be interesting to know if these phenomena were investigated objectively during the war?

Steve.

[Giorgio N]

9 hours ago, Graham Boak said:

 The Italian 12.7 round was actually explosive, and was generally thought to be ineffective because of that.  The small amount of explosive carried would explode on contact with the skin rather than hitting hard.   If Allied pilot armour was being penetrated in the Desert war then it was probably fired by an MG151

 

 

Generally only 1 in 5 rounds was explosive, the mix most commonly used having 2 balls, 1 tracer, 1 AP and 1 explosive round.

 

[Crayons]

I fully expect to be chased out by a mob, wielding pitchforks and brands of fire as I'm not a wingy thing person, I can fly/have flown several Huey's if that saves me from the unruly masses.

 

Pretty much all of my service was spent on vehicles using the m242 Bushmaster, so I'll take a cannon over an MG any day for engagements.

 

When as in aerial combat the LOOF is very narrow due to speed and angles, a heavier, harder hitting projectile, be it ball, tracer, ap or HE and all the derivatives in between is much more advantageous as it is in ground fire. A blend of smaller calibre and heavy cailbre is kind of the best of both worlds (for the purpose of actually getting hits). Now, it comes with a trade off, ROF (cannon specific). With modern aircraft, combat or otherwise, one round anywhere be it MG, cannon or AA it is going to do damage (crippling or otherwise, the aircraft in 99.9% of scenarios is out of the fight), the old wingy things with the their cables and handful of hydraulic lines, didn't suffer from the same issues. The Soviet era BUK is a classic example, the missile itself doesn't hit the aircraft, but explodes near it, sending a metric Fton of shaped shrapnel into the target aircraft. Damaging vital systems and ending the flight abilities of the aircraft. HE cannon rounds did/do a similar thing, utilising shrapnel to do the damage. Now, would they penetrate the rear armour of a pilots seat, no, not their design, but I bet sure as, that pilot is out of the fight for X amount of time healing broken bones from the explosion concussion.

 

Never look at WWII era gun cam as being the first part of the engagement, the bit they show of the enemy going down in a hail of mg bullets is to win the hearts of the people, it is rarely truthful.

 

Also, look at the reasoning and performance of the weapons selected and the thoughts/doctrine of the time, it isn't a random theory someone conjures up after a hard night on the single malt.

 

My two cents, no change or refunds given.

 

[PatG]

The incident recounted by Tom Neil involved combat with Macchis 202's where the round penetrated both the armour plate and the pilot and ended up somewhere in the bowels of the cockpit, so this would suggest an AP round from the 12.7mm mg.

 

The pilot involved was Pat Lardner Burke who subsequently recovered from his injuries and this incident is also recounted on various other web sites so presumably this adds credence to the incident, or has it just been retold without further investigation?

 

For example:

 

"Pat’s Squadron was involved in one of the biggest dogfights seen over Malta. 18 Italian Macchi were intercepted whilst they were escorting their bombers bound for Malta. Flying Hurricane BD789 he engaged and shot down a Macchi 202 near Dingli, but as he was engaging the Macchi another one engaged him from behind. The result was a 12.7 mm bullet from the Italian fighter which penetrated his seat armour and passed out of his chest.

With a punctured lung and bleeding heavily, Pat drew on all his skill and managed to land his Hurricane at his aerodrome on Malta. A fellow officer, Tom Neil witnessed his landing, ran to the aircraft and pulled Pat free from the damaged Hurricane.

 

Pat was laid onto a stretcher, an ambulance took him to hospital. Tom Neil then took time to inspect Pat’s hurricane, several bullets that had hit the side of the aircraft behind the cockpit. However Tom was shocked as he noted one had punched a hole in the armour-plate and penetrated the back of the seat, where it had passed right through Pat and carried on through the cockpit’s dashboard and then through some more armour-plate in front. Neil and the other pilots in the squadron were literally shaken by the knowledge that the Italian’s were using some very powerful ammunition".

 

Not definitive but the source is 'The Observation Post - South African Military History' web site. (https://samilhistory.com/)  so worth considering.

 

Pat.

[tempestfan]

As far as I'm aware, explosive rounds (at least in the smaller calibres) are intended to punch large holes and/or distribute splinters, in order to ideally cause as much damage to airframe and systems around the point of impact as possible. An AP round would pierce armour plate, but only make a relatively small hole. In order to be effective, it would need to hit a vital part of the aircraft on its path, or the pilot.

[Mark Harmsworth]

I may well not know what I am talking about (surprising, I know) - but weren't there examples of Luftwaffe planes returning to northern France during the BoB decorated with dozens of little bullet holes but no real damage? Or is that just a myth?

Mark

[alt-92]

17 hours ago, PatG said:

Interestingly the US, with some minor exceptions, never used the 20mm cannon and preferred the 0.5 inch Browning instead

Mostly because they could not get their M1 variant of the Hispano Suiza 404 (itself a further development to replace the Oerlikon-based variants) to work properly, delaying the introduction. Similar issues with early versions of the HS.404 in UK service were the reason why the Mk.Ib trial with 19 Sqn was such a bad experience.
The US armed forces then reworked the British Mk.II Hispano into the AN-M2* but that also proved problematic, one of the reasons the P-38 had a recocking mechanism in the cockpit for dealing with misfires.

 

It should also be noted that autocannon were pretty rife in the late 1930s, especially with the French. They had those long-barreled 20mms as defensive armament on the LeO 451 and the intended armament of the SNCASE 1000 ground attack aircraft was 4x HS.404s.
Then there's the Danish 20 and 23mm Madsens, used by both the Danish AF and Dutch LVA. 
 

47 minutes ago, Mark Harmsworth said:

I may well not know what I am talking about (surprising, I know) - but weren't there examples of Luftwaffe planes returning to northern France during the BoB decorated with dozens of little bullet holes but no real damage? Or is that just a myth?

Well, the ones that don't return tend not to get much notice, do they

 

 

anyways:
https://web.archive.org/web/20171030102939/http://quarryhs.co.uk/WW2guneffect.htm

 

The original idea the USN had was getting sufficient boom on target, and three 50cal M2 Brownings could be replaced for less weight overall by one cannon for equal firepower. 

 

_{*AN prefix here means Army/Navy, so both services would use the same weapons systems.} 

[tempestfan]

...and it might be added (but @alt-92 did to some extent) that the USN apparently was rather keen on getting 20mm's in their fighters - -4B, -5, and about all early jets - Banshee, Demon, Crusader,Panther/Cougar, Tiger...

[PatG]

There are indeed many photos showing Luftwaffe bombers riddled with .303 bullet holes but which managed to return safely, so if we'd had cannon or the .5 inch Browning the results may well have been different.

 

In the case of Lardner-Burke the round made a small hole in the armour plate after which it went all the way through him before ending up somewhere in his cockpit, which suggests an AP round.

 

Interestingly in Korea the US still used .5 inch Brownings in the Sabre compared with the 20mm and 30mm guns employed by the Mig15s so which option was better I wonder?

 

Just wonder why we didn't think to use the .5 inch Browning in BoB Spitfires and Hurricanes, say 1 per wing plus two .303's given the problems we had at the time developing the Hispano cannon which proved to be very troublesome with numerous jams/blockages?

 

And of course the .5 inch Browning was subsequently used much later in the 'e' wing to great effect.

 

Pat.

Edited April 2 by PatG
extra information

[alt-92]

11 minutes ago, PatG said:

There are indeed many photos showing Luftwaffe bombers riddled with .303 bullet holes but which managed to return safely, so if we'd had cannon or the .5 inch Browning the results may well have been different.

Again. 
The ones that do not make it 'home' you will not read or hear about. 
Survivorship bias.

 

 

11 minutes ago, PatG said:

Interestingly in Korea the US still used .5 inch Brownings in the Sabre compared with the 20mm and 30mm guns employed by the Mig15s so which option was better I wonder?

As said, the 20mm cannon development in the US took quite a circuitous route, from the M2/ M3 to a Colt Mk.12 and eventually a M39 (based on the Mauser MGs) intended for the Sabre that was just a little too late to see action.

MiG-15s used 23mm NRs & a single 37mm (makes sense as a bomber interceptor), with the 30mm variant only introduced on the MiG-19 so outside Korean War scope.

 

 

11 minutes ago, PatG said:

Just wonder why we didn't think to use the .5 inch Browning in BoB Spitfires and Hurricanes, say 1 per wing plus two .303's given the problems we had at the time developing the Hispano cannon which proved to be very troublesome with numerous jams/blockages?

 

The .50 was not in use in the UK (well, barely). 
So then logistics comes into play.  If you decide to take a stop-gap measure by introducing that .50 you also have to adapt not only the aircraft itself (as the .303 browning is smaller and lighter) but also you have to arrange for a separate ammunition flow. 
And since the intent was always to use the Hispano 20mm, the eventual use of the .50 in the E-wing Spits is mostly because by that time there was plenty of supply around (and it nicely got rid of extra weight in the outer wings).

[PatG]

I guess hind sight is a wonderful thing but if the RAF had opted for the .5 inch Browning over the 20mm Hispano then in theory Spitfire and Hurricane 1's could have carried this more potent weapon during the BoB and achieved more kills with fewer 'riddled' bombers returning to their French bases.

 

The effect of 4 of these weapons, 2 per wing in the inner positions, would have been more effective than 8 of the .303's I suspect and added weight to Bader's preference for mg's only in his aircraft.

 

There again at the time the prototypes of the Hurricane and Spitfire flew 8 mg's was considered to be quite a heavy armament and the prospect of enemy aircraft having armour plate to protect vital areas had not really been considered or factored in.

 

Pat.

[Graham Boak]

There has been continued discussions for many years  (including in the 1950s Tail Gunner magazine for ex-RAF gunners) regarding the respective merits of four 0.303 and two 0.5s.  There seem to be two main factors affecting RAF procurement.  The first being trials held in the early 1930s which came to the conclusion that the 0.5 Browning offered no great advantage over the 0.3,.  In order to help stocks and inter-service compatibility, it was decided to licence build the Browning 0,3 but in 0.303 form.  It was recognised that to get the required weight of fire against bombers eight guns would be required in fighters, two or four in turrets on larger aircraft.  With hindsight, it was clear that this trial showed the effect on fabric-covered aircraft, but the stressed-skin designs that actually featured in the war.  Against such stronger structures the 0.5 can be assumed to be more effective, as proven.

 

Then the RAF encountered the Hispano and were converted to wanting this, four in fighters and two to four in bombers.   Producing suitable turrets for future bombers proved much more difficult than expected, and the pressures of war lead to the future bombers being cancelled anyway.  This meant that fighters were to be well armed (four proving two too many for the prewar fighters) but the bombers underarmed as the war proceeded.  This was recognised early and work was done on 0.5 turrets, not entirely satisfactory from their size but the BP design was passed over to the US and contributed considerably to the design of the successful Sperry.   However the main problem, and the second major factor, with the 0.5 became not its problems of fit but the availability: once the US entered the war they were not available in sufficient numbers to standardise on, because priority went to meeting the huge demand for US forces.

 

However, as far as the BoB was concerned, it was largely fought with only lightly armoured aircraft, and the 0.303 shot down an awful lot of aircraft, not just then but later too.  The plans were of course to have interceptors armed with 20mm, but the Whirlwind was slow in getting into production and service.

[gamevender]

Just as a bit of an aside, the Bell P-39 was armed with a US made 37mm cannon in the nose and was available at the start of the war. I know the Airacobra gets a bad rap for a variety of reasons, but someone in the design team thought a cannon was a good idea back in 1938. Just sayin'...

[Graham Boak]

Not available at the start of the war, and not even in time for the BoB, which when this discussion largely concentrates on.  By the time it entered service the RAF, Luftwaffe, VVS and IJN all had major fighters with cannon.  And the French, of course, the first of all.

[dogsbody]

Years ago, I read that the standard .303 steel-jacket rifle round could penetrate 1/4 inch of armor plate, if it hit at a 90 degree angle. 

Now I don't remember where I read this and I can't find it now. Does anyone else know of this?

 

 

 

 

Chris

[alt-92]

Some more gasoline on an open fire:
 

 

[PatG]

If the UK had obtained a license to manufacture the .5 inch Browning early on and then opted to use it instead of waiting for the Hispano cannon to become effective then it's quite possible that Spitfire and Hurricane 1's could have had them in the BoB even if it was one per wing along with two .303's, but as I say hindsight is a wonderful thing.

 

As for Mr Holland's belief that the 20mm cannon in the Bf109E was a 'major advantage' I'm now even more disinclined to agree with this notion as a wide spread of fire from 8 mg's gave the average pilot far more chance of actually putting a hole in something, particularly as pilots on both sides were 'average' in the main with only a small few mastering deflection shooting. As such the usual pareto law would seem to apply where by the majority of aircraft shot down were done so by a relatively small percentage of pilots on both sides.

 

Pat.

 

 

 

 

[Circloy]

1 hour ago, dogsbody said:

Years ago, I read that the standard .303 steel-jacket rifle round could penetrate 1/4 inch of armor plate, if it hit at a 90 degree angle. 

Now I don't remember where I read this and I can't find it now. Does anyone else know of this?

 

 

 

 

Chris

That is very probable. I recall being surprised when I found out that .303 was a size still in use during the 80's & 90's for proof testing of armour plate.