What if you could start from scratch and design your own? What would it look like? See:

http://www.quarry.nildram.co.uk/ideal.htm

Tony Williams: Military gun and ammunition website and discussion
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Tony Williams: Military gun and ammunition website

Tony - thanks for the info about German 20mm and 30mm shells which always fascinate and baffle me at the same time !

Ideal aircraft armament ? Call me biased but it'd just be the Mosquito FBVI, maybe with .50 Brownings instead of the .303s....

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"Stand by to pull me out of the seat if I get hit" - Guy Gibson

While your discourse (Tony Williams) on aircraft ammunition was interesting it ignored the important question of muzzle velocity completely (among other things). This, ancedotially, appears to be of high importance in determining the effectiveness of aircraft weapons. Low muzzle velocity guns and cannon seem to have been generally derided by pilots as far less desirable than high velocity ones even if it meant fewer weapons of smaller caliber mounted.
This is one reason the .50 Browning remained in serivce so long. It had a flat trajectory and high velocity round making it relatively accurate. Many German pilots late in the war continued to prefer the MG 151 20mm cannon to the Mk 108 30mm simply because the later was so inaccurate except at close range. Certainly, this is why the MGFF and similar weapons fell out of favor early in the war. Their lack of velocity made them of marginal value in aerial combat.
I think it is far more important that the rounds hit the target than if they do slightly more or less damage.
If the latter was true most US fighters would have been armed with 37mm cannon (most had some sort of planning done to do this) rather than .50 machineguns as but one example.
Ammunition carried is also important in determining which aircraft weapon to choose. Many US Naval pilots in the early years of the war were very vocal about the reduced ammunition the F4F-4 carried versus the F4F-3. They would have rather had only 4 .50 machine guns and more ammunition per gun than the increased firepower of the 6 .50 machine guns of the F4F. Thus, there is a trade-off between weapon size, rate of fire and, ammunition carried.
So, there are several views that can be taken on this subject beyond the effectiveness of each individual round.
There is the effect of multiple hits. In the extreme one might look at the 8 .303 battery of many early war British aircraft. The effect of these guns was to simply saw the enemy aircraft up through massive numbers of hits.
The .50 could reach out further and do the same.
Cannon with explosive shells could blow an aircraft apart but, with few hits bigger aircraft often survived.
As to wall thickness of the shell, which is to be prefered, blast or fragmentation? I would think fragmentation would be prefered to blast. The latter is a cube function over distance and therefore unless contained has very little effect over any distance from detonation. Fragments can travel (as a square function for their energy) over far greater distances and do damage. This is certainly the prefered choice in field artillery.
So, the question you pose is a very difficult one to answer. I think that multiple fast firing guns with plentiful ammunition and reasonable effectiveness are far better choices than one or two very heavy cannon with moderate rates of fire and small ammunition loads in aerial combat regardless of target. Now, if an aircraft is specifically being designed to counter a specific threat this might change but, the best all 'rounders are ones with 6 - 8 .50 machineguns, 4 20 mm cannon or, some mix of the two not some heavily laden aircraft with slug throwing low velocity 30mm cannon.

In 1945 the 2cm was not preferred over the 3cm weapon. The 2cm was standard equipment in the Bf 109 G series and the 3cm in the K through the nose. The Fw 190A-8 and A-9 was fitted with 4 standard 2cm weapons and only with the heavier Sturmböck of the 3 Strumgruppen did the 3cm come into play. In 1945 the 3cm was standard on the Bf 110G-4 nf and the Me 262 fighter versions.

Simply put the change in the German Luftwaffe came about in Janaury of 1945 when the bulk of the fighter forces from the Reich battled for the last air battles on the ost front and Berlin. There was no need for the heavier 3cm wepaons to be fitted as there were no heavy Soviet bombers to form attacks against.

Backing up in the fall of 1944 many of the Fw 190 pilots of all the Reich defence units reduced the 2cm weapons to two so they could have more manueverability agsint P-51 escorts. This was a pilot preference and there still was usually a heavy gruppe within the geschwader that retained the normal armament. And in fact for III./JG 301 many of the A-8's were R-2 versions with the heavier 3cm for dropping the US heavy bombers.

So I am not sure where your statement of preference of the 2cm over the 3cm came from.
The only notation I have is an old one from NF ace Rudi Thun of NJG 5 where his gruppe experimented with the 2cm long rods in the upper nose and changed back to the heavier 3cm cannon soon afterward......

~E

Pardon? My article includes the following statement: "The muzzle velocity would need to be reasonably high in the interests of short flight time (important for scoring hits, especially in deflection shooting) and maximising the effective range." My 'ideal' proposal has a muzzle velocity of 850 m/s, compared with the .50 M2 of around 890 m/s - not a huge difference. If you look at the article which analyses and compares actual aircraft guns (http://www.quarry.nildram.co.uk/WW2guneffect.htm) you will that muzzle velocity is given equal status with projectile weight in calculating effectiveness. That is hardly 'ignoring it completely'.

Neither is there much point in repeatedly hitting the target with small projectiles which do little damage. As in most things, it's a proper balance of characteristics which is required.

Indeed. They probably needed more ammo because they had to shoot so much of it into the target to have any effect [img]smile.gif[/img] As it happened, they found that four .50 weren't enough and all subsequent .50 M2-armed fighters had six of them.

Of course, that's what makes the debate interesting!

Some German bombers made it back to base despite having hundreds of .303 bullet holes in them. The RAF was desperate to get the 20mm into service because of the difficulty in shooting planes down with the .303.

And would have survived multiple .50 hits even more easily. The 20mm Hispano ballistics were pretty much the same as the .50 at effective fighting ranges.

An interesting and complex question. It is clear that the Luftwaffe formed the view that blast was more important, but that doesn't mean that the M-Geschoss didn't produce fragments. This is from 'Flying Guns: World War 2' (by Emmanuel Gustin and myself) and concerns information provided to me by an American who witnessed the test:

"after the war, the Americans test-fired an MK 108 HEI shell into the tail of a B-24 at a typical angle, characteristic of a tail interception by an Me 262. The "spray" pattern of very high velocity, very small fragments cut most if not all of the control cables and many of the longerons. It was assessed that the tail would have separated if the plane had been in flight; a performance which made a great impression on the observers."

The six or eight .50 did the job they needed to (which was essentially against fighters rather than bombers). However, the penalty was a considerable weight of armament. Four 20mm Hispano cannon were approximately twice as destructive for about the same weight; cannon, because of their explosive/incendiary shells, were simply more efficient.

Tony Williams: Military gun and ammunition website and Discussion forum

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Tony Williams: Military gun and ammunition website

Tony, can I just ask your opinion - which was the better/best, Hispano 20mm or Mk108 3cm ?

I know that one immediately thinks the German gun must be better because of the greater projectile weight but I know that the low muzzle velocity meant that the German pilots had to get in very close for a kill.

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"Stand by to pull me out of the seat if I get hit" - Guy Gibson

? best ?

for which application. obvious the 2cm had the better range and the 3cm had the greater destructive power. Martin I've covered this over the past two years on these forums with personal interviews from Sturmgruppen pilots. The 2cm was to take out the tail gunners position and then once freed from their harm the 3cm would 'open up' the bomber like a meat cleaver. Have cine films to prove the ugly efficency of this weapon

Sorry, did not want to answer for Tony........since your question was posed to him........oh insert foot in mouth

Ah but hang on, Erich - I said 'Hispano' not MG151, big difference !

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"Stand by to pull me out of the seat if I get hit" - Guy Gibson

yes you are correct, but as we have chatted the 3cm Mk 108 was a bomber killer and that was envisioned for the cannon straight up.........
not wanting to take away from the Hispano as it was lethal enough

The Hispano's much higher muzzle velocity made it far better against fighters. The MK 108 was death to heavy bombers. As Erich said, it's horses for courses.

If you look at my article on the 'ideal' WW2 armament, you can see that I prefer the 20mm for most purposes, but would supplement this with 30mm if heavy bombers were a problem. The 30mm loading I would go for, however, would fire a lighter shell at a higher velocity than the MK 108, losing some destructiveness to gain a better all-round performance. Interestingly, that is exactly what the British and French did with the 30mm Aden/DEFA cannon. These were direct developments of the MK 213 and originally had the same heavy shell/low velocity combination, but this was changed to a lighter, faster loading in the interests of increasing the hit probability.

Tony Williams: Military gun and ammunition website and Discussion forum

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Tony Williams: Military gun and ammunition website

Thanks for clarifying that, gents ! ( BTW, I wonder how a bomber would have stood up to the Hispano..? )

I'll stick to my ideal : a FBVI with 4xHispano, 4x.50s and maybe a few rockets under the wings for good measure. Might need to uprate the Merlins a little to cope

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"Stand by to pull me out of the seat if I get hit" - Guy Gibson

It wasn't my intention to start a war on this subject, just to expand the debate. Tony's system is a decent first approximation of aircraft weapons effectiveness. I certainly will credit him with making an empirical effort on the subject.
As another question to Tony: Have you considered the explosive filler type for each round? This greatly effects both the blast and fragmentation effect of a round. Some of the Japanese rounds, as an example, used black powder and picric acid as their explosive. This greatly reduces the effect of these rounds through the use of a low velocity explosive. In the same vein, as I pointed out, blast is a cube function while fragmentation is a square function. Thus, a better approximation of blast might be a square root of filler weight than simple linear weight as an approximation. Twice as much explosive does not equal double the blast effect. Fragments fall off as an inverse square function approximated by the equation: .014x^2 - 4.82x + 473.12 for heavy walled shells and .014x^2 -4.03x + 352.18 for thin walled. These give a predicted number of fragments from a round of a given size where x is the size in millimeters.
The round so long as it is cast as a single piece, regardless of wall thickness, almost always comes apart much as a banana peel. There are a few large long fragments that are fairly heavy and a large number of small fragments that form in the cracking areas between the larger ones. The later are of little value casuality-wise as they lack the necessary weight and velocity to cause much damage. Now, these might be more effective against aircraft where the surfaces are less prone to inelastic collisions but, I really haven't done much on that particular area.
I would also ask Tony if he has taken into account typical ammuniton mixes. For example, the .50 includes a high explosive round (RDX or Amatol filler), a incendiary round (RDX and powdered aluminum) and a tracer round. Even the rifle caliber aircraft weapons have such rounds. Is this accounted for?

How about swapping the Merlins for RR Griffons as with the Spitfire?

Good idea - let's call it a Hornet !

http://www.mikegrantdesign.com/modelpix/DHHornet.html

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"Stand by to pull me out of the seat if I get hit" - Guy Gibson

Yes, the effectiveness tables take into account typical belt mixes as far as Emmanuel and I could determine them. So the German 20mm values take into account the fact that only some of the shells were the high-capacity M-Geschoss etc.

German, Italian, Japanese and even Russian .50 (12.7-13mm) had some HE shells in the mix and these are allowed for. The US .50 didn't use HE in WW2, however, only incendiary, AP and later API. This has been allowed for but the API carried only a small quantity of incendiary material (less than 1 gram).

Different types of explosive have not been accounted for, as the fillings for a particular did tend to vary through the war. 'Flying Guns: WW2' contains data tables on the actual fillings of shells 12.7-75mm, with a comparison table of the relative effectiveness of different types of HE.

Tony Williams: Military gun and ammunition website and discussion
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Tony Williams: Military gun and ammunition website

Ironically I saw a show on Discovery about this exact topic. It compared the Spitfire and the 109 in 4 different catagories, one being armament.

The most interesting part (to me) was when they got a .303 machinegun and shot it at a piece of 109 wing, and then got a 20mm AC and shot it at a piece of Spitfire wing.. accuracy and velocity aside, you'd need to pump as much as a hundred or more .303's into a fighter to down it and maybe five 20mm to do the same, of course not taking into account "lucky shots". Plus, having armour able to stop a .303 round is possible; armour to stop a 20mm round is almost impossible, atleast on a fighter. I would rather have two 20mm than 8 .303's.

I always had an affinity for R4M and similar anti-bomber rockets, though I've only ever personally heard of them being used on Me-262. Were they used on Fw-190 or Bf 109 as well?

I didn't see this show...was it the same one as the one that compared the sherman to the Tiger on BBC?

If so it should be taken with a wee grain of salt.

Those numbers you quote about peppering a wing full of 0.303 rounds are not quite well...realistic!

The most important aspect the show would not have considered (correct me if I am wrong) would have been: fighters do NOT shoot at one another whilst they are both stationary.

Lets ponder on that a sec,

A 109 on the ground gets hit with 2 bursts of Browning, say being hit in the wing or tail a half dozen times, ok there are a few holes in it and you might get leaking fuel.

In the Air a 109 with the same hits gets subjected to G-Forces depending on what manouver it is trying to pull whilst evading its attacker.
Say its in an inverted dive and it receives the hits in a critical structure, say joining the wing to the fuselage. Your wing would tear off the plane and a relatively minor hit would be a serious problem! [img]tongue.gif[/img] Not withstanding a COUPLE of hits with Canon in the same spot would probably torch the fuel tanks as well as rip the wing off

Back to the armament question though!
Willy M, was adamant he could not match the firepower of the hurricane or P-47 as his original design (which was first deployed in the Spanish civil war) had reached the zenith of its development by the time the p-47 had made its debut. The 109 was NEVER designed to intercept highly armed and escorted Bombers over long range. As development for the FW190 was slow, the 109 stayed on, and when the FW190 proved disappointing at altitude with its non-radial opponents the 109 continued to be modified wayyy past its sell-by date.

As Willy once said when asked to upgun his precious 109:
[ 26. January 2004, 04:29 AM: Message edited by: BratwurstDimSum ]

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I think "Willy's" problem and the German aircraft industry's in general was that they were limited by the engines they had available to them. The German engines typically had a lower horsepower to weight ratio than, particularly, British aero engines and to a lesser extent US engines, lacked really top notch superchargers and, turbo chargers (something lack of materials made impossible to mass produce in Germany). Coupled with lower grade aviation fuel and, the widespread use (late war) of nitrous oxide and Methanol / water boosting agents (weight and volume problems) the Germans had to trade something (range and armament) to get performance on par with Allied aircraft.