Aircraft armament....

[Lucky13]

Which was the best aircraft fitted gun/cannon of WWII? And, why did the RAF stick with .303, what was their reasoning behind, why not go for bigger like .50's?

 

[Doubl3Ac3]

if i had to guess it was for more ammo. the .303 could do a fair amout of damage with a short burst. In the same matter the .50 could do the same in just 1 shot. the difference is size and weight, the .303 is alot lighter and smaller and is alot easier to lead a target with compared to the .50 which is alot heavier and take alot more skill to lead a target

 

[DerAdlerIstGelandet]

I think best weapon depends on what you are gunning for.

As a bomber killer I would want a larger caliber weapon such as the ones manufactured in Germany: MG FF 20mm Cannon armed with high explosive Minengeschoss, or the MG 151/20 20mm Cannon armed with high explosive Minengeschoss, or even the MK 108 30mm Cannon armed with high explosive Minengeschoss.

If I was doing just regular air to air combat with other fighters or light aircraft the US .50 Cal was just fine for the job and that is what I would want.

 

[drgondog]

I think best weapon depends on what you are gunning for.

As a bomber killer I would want a larger caliber weapon such as the ones manufactured in Germany: MG FF 20mm Cannon armed with high explosive Minengeschoss, or the MG 151/20 20mm Cannon armed with high explosive Minengeschoss, or even the MK 108 30mm Cannon armed with high explosive Minengeschoss.

If I was doing just regular air to air combat with other fighters or light aircraft the US .50 Cal was just fine for the job and that is what I would want.

Chris - I'm pretty much with you on all points. I would like to have seen 51s with four of the MG151/15 or 20mm as the standard configuration. Suspect there would have been more German a/c shot down but difficult to prove.

As to a 303 being easier to 'lead'?? - I would doubt it. I don't understand the logic on that comment.

The 50 had 5x more mass and superior Ballistic coefficient so would experience less velocity loss and drop in trajectory for meaningful ranges and far more punch per round. If you are referring to a hand controlled waist gun 50, maybe the recoil would be more difficult to manage for a leading/tracking deflection shot but that would be pretty subjective.

 

[HoHun]

Hi Lucky,

>Which was the best aircraft fitted gun/cannon of WWII?

The MK 108.

>And, why did the RAF stick with .303, what was their reasoning behind, why not go for bigger like .50's?

They did not expect to fight armoured aircraft, and they overestimated the penetration power bullets have after passing through the aluminium skin of an aircraft.

Here is a firepower comparison, based on total muzzle energy (kinetical plus chemical, based on the equivalent of the shell's chemical content if it were TNT). The list is sorted by firepower per weight (including guns, ammunition and belting/drums), which is the most important limiting parameter for an aircraft gun battery. The ammunition supply is chosen to give the same total muzzle energy total for all rounds. The reference weapon is the US 12.7 mm Browning M2:

1x MK 108 - 87 rpg - 111 kg - 221% firepower - firepower per weight: 900%
1x MK 103 - 75 rpg - 210 kg - 180% firepower - firepower per weight: 387%
2x MG 151/20 (MX) - 187 rpg - 164 kg - 124% firepower - firepower per weight: 342%
2x MG 151/20 - 207 rpg - 172 kg - 112% firepower - firepower per weight: 294%
2x Hispano V - 212 rpg - 188 kg - 109% firepower - firepower per weight: 262%
2x Hispano II - 206 rpg - 201 kg - 94% firepower - firepower per weight: 211%
3x MG-FF - 149 rpg - 235 kg - 103% firepower - firepower per weight: 198%
5x MG 151 - 239 rpg - 428 kg - 97% firepower - firepower per weight: 102%
10x MG 131 - 311 rpg - 413 kg - 93% firepower - firepower per weight: 102%
8x ,50 Browning M2 - 250 rpg - 452 kg - 100% firepower - firepower per weight: 100%
25x Browning ,303 - 399 rpg - 549 kg - 96% firepower - firepower per weight: 79%
25x MG 17 - 406 rpg - 596 kg - 95% firepower - firepower per weight: 72%

The list is a bit "uneven" because I tried to avoid "fractional" guns in the batteries Except for the rifle calibre machine gun batteries which would have been a nightmare to fit into a typical WW2 fighter, all of these batteries could have been realistically used in most fighter types of the era.

In my opinion, the question is not so much one of the best gun, but one of the best battery. I'd mix different weapon types, for example one nose-mounted MK 108 and two wing-root mounted MG 151/20 with MX shells in the mix. (The data is based on typical belting patterns for all guns.)

1x MK 108 - 87 rpg - 111 kg - 221% firepower - firepower per weight: 900%
2x MG 151/20 (MX) - 187 rpg - 164 kg - 124% firepower - firepower per weight: 342%

Total battery: 298 kg - 345% firepower - 523% firepower per weight

The advantage of the mixed battery is that you have extremely high firepower at short ranges and under good conditions (with a non-manoeuvering target) thanks to the MK 108 and still decent firepower at longer ranges due to the higher muzzle velocity of the lower fire-power MG 151/20.

Regards,

Henning (HoHun)

 

[renrich]

The later model Spits did go with the 50 cals mixed with cannon. I also don't understand the comment about easier to lead with 30 cal. The MV of the two rounds was about the same and the BC of the fifty was so superior that the downrange velocity of the fifty was much faster and flatter shooting. I think the only reason the Brits used the 303 as long as they did was because that is how they started out and perhaps could not change in a hurry because of the redesign necessary and perhaps could not get the guns easily for the 50 cal. They also had a propensity for wanting a lot of guns and screwed up the F4F4 by insisting on a six gun battery instead of the four in the F4F3.

 

[pbfoot]

here is the reasoning for the 8 303's in Brit aircraft
" after the Schneider races of 31 and the resulting speed record tacticians concluded that at such speeds a fighter would only have one chance to destroy its prey - the first attack-and that chance would last precisely 2 seconds . Ballistics experts showed a battery of 8 machine guns firing 1000 rounds a minute each would be needed to destroy a bomber in 2 seconds .Senior officers brought up on 2 syncronized forward firing Vickers guns raised their eyebrows . WC AT Willliams and SQn Ldr later Air Marshall Sir RS Sorley however took up the cause of the 8 gun fighter and when Williams its ardent and original champion died in 1934 it was Sorley more then anyone else who was responsable for its adoption by the RAF.
It was the confluence of this tacticle need the work already being carried out by Camm and Mitchell the arrival of the Merlin and the browning machine gun that bore fruit in Specification F.5/34 (revised later to F36/34) The American Browning was a "first class weapon " with a rate of fire of 1260 rpm .A perfect example of intimate collaboration between airman and designer was Sorleys's test showing that in order to achieve a lethal density of bullets the Brownings would have to use their maximum rate of fire . This meant that they would have to be clear of the propellor arc which in turn meant the the wings would require speciak strength and rigidity - which Camm and Mitchell promptly undertook to provide
From AHB/II/116/17 ,p82 ,fn2

 

[HoHun]

Hi Pbfoot,

>and I aint typing any more unless requested

Interesting stuff, keep it coming please!

Regards,

Henning (HoHun)

 

[lesofprimus]

There was also the point that the Brits had an obscene amount of .303 ammo laying around, so that if they changed out the caliber of gun, all that ,303 ammo would go where???

 

[pbfoot]

Hi Pbfoot,

>and I aint typing any more unless requested

Interesting stuff, keep it coming please!

Regards,

Henning (HoHun)

I added the remainder to the original post

 

[kool kitty89]

les, that's true, but it should be noted that there were shortages of the most effective .303 rounds, particularly the "De Wilde" incendiary types (B.Mk.VI, and later B.Mk.VII) early in the war. A large amount of ball ammo was aparantly used due to shortages of more effective types.
THE BATTLE OF BRITAIN

The 'De Wilde' bullets were first issued in June 1940 and tested operationally in the air battles over Dunkirk. Their improved effectiveness, coupled with the fact that the flash on impact indicated that the shooting was on target, was much appreciated by the fighter pilots. It was at first in short supply, and the initial RAF fighter loading was three guns loaded with ball, two with AP, two with Mk IV incendiary tracer and one with Mk VI incendiary. Another source for the Battle of Britain armament gives four guns with ball, two with AP and two with incendiaries (presumably Mk VI) with four of the last 25 rounds being tracer (presumably Mk IV incendiary/tracer) to tell the pilot he was running out of ammunition. It is not clear why ball was used at all; presumably there was a shortage of the more effective loadings. (By 1942 the standard loading for fixed .303s was half loaded with AP and half with incendiary.)

And the .303 would still have plenty of use on the ground.


There's an interesting new article on Tony Williams' site on British aircraft armament: http://www.ww2aircraft.net/forum/weapons-systems-tech/raf-guns-ammunition-15659.html#post420628

 

[HoHun]

Hi Pbfoot,

>I added the remainder to the original post

Thanks!

>This meant that they would have to be clear of the propellor arc which in turn meant the the wings would require speciak strength and rigidity - which Camm and Mitchell promptly undertook to provide

I'm a bit sceptical about the "strength" bit ... at least the Spitfire was designed for just two machine guns per wing, and the installation of the additional two not originally foreseen by the designer was actually very awkward and ballistically inefficient.

>From AHB/II/116/17 ,p82 ,fn2

Hm, I have to admit that I'm unable to decode this ... some RAF internal history document perhaps?

Regards,

Henning (HoHun)

 

[kool kitty89]

It should be noted that the British did have a competent heavy machine gun in the .5" Untitled Document which was somewhat lighter than the Browning though it fired the less powerful 12.7x81 Vickers round. (this also would have meant lower recoil forces on the wings of the smaller RAF fighters)

The reasoning behind staying with the .303 was from:
RAFHS 08

Vickers was in the process of developing a scaled-up version of their .303" MG, chambered for a new .5" (12.7 mm) cartridge. This was produced in three versions for army, naval and aircraft use and was tested by the RAF in the mid-1920s against the new .50" Browning heavy machine gun, which was bigger and more powerful. The conclusion was that neither offered sufficient advantages to replace .303" MGs, since the slightly bigger hole they could punch wasn't adequate compensation for their greater size and weight and their lower rates of fire. The Swiss Oerlikon 20 mm cannon, developed from the German Becker of the Great War, was also tested in the late 1920s and early 30s and proved more promising since its explosive shells could do a lot more damage than just punching bigger holes, but it was big, heavy and slow-firing.

Of course this would be ignoring the larger incendiary content of the .50 round even if you exclude the armor variable from the equation. (it would also do greater damage to structural components)
They instead made the choice, as many know, to go straight to 20 mm cannon if a harder hitting weapon was necessary, but the Hispano, while an excellent weapon was not ideal for all the situations a HMG woud be useful. (particularly in smaller fighters and for defensive armaments) So they got stuck with mixed armaments (retaining 4x .303 guns + 2x 20mm on Most Spitfires) and almost exclusively the .303's in defensive (flexible/turret) instalations.


Incedentally both the Italian 12.7 mm aircraft guns and the IJA Ho-103 (a derivative of the Browning) used the 12.7x81SR ammunition, the semi-rimmed export version of the .5" Vickers round.

 

[renrich]

Really interesting stuff PB, KK, etc. Many thanks. I read an article in "Air and Space" a while back that ties into Pb's post which said that the two second burst would amount to 270 hits(or something like that) which was what it would take to bring down a bomber. I would like to hear from those in the know how the recoil from the various weapons load would impact the fighter. I have a reference that mentions that in a F8F if the cannons on one side had a stoppage it really introduced a yaw component.

 

[Glider]

I think its worth remembering that when the decision was taken to arm the RAF fighters with 8 x LMGs, this was considered by all forces to be a pretty heavy armament.
The 109 of the same period had 3-4 x LMG, The Italians had 2 x HMG, The Japanese 2 x LMG, the USA often had 1 x HMG 1 x LMG, The French had 1 x 20mm and 2 x LMG.
Against this, 8 x LMG wasn't to be sniffed at.

Its also worth remembering that before the war that the UK knew that the 303 wasn't a long term solution and that the 20mm Hispano was the way to go. The problem was of course, that the 20mm took longer than expected to be made reliable.

As for the HMG, I dont disagree that it was the best weapon for bomber defence and was sufficient for attacking other fighters and smaller bombers. However, if you had to go up against a 4 engined bomber then I believe it would have been lacking.

 

[renrich]

The US Navy in the Pacific felt that the 50 cal was quite effective aginst surface ships up to the size of and including DDs. There were instances of patrol craft and small coasters being disabled by AC armed with 50 cals.

 

[pbfoot]

. I would like to hear from those in the know how the recoil from the various weapons load would impact the fighter. I have a reference that mentions that in a F8F if the cannons on one side had a stoppage it really introduced a yaw component.

Not in the know but heres a good little tale from JP Coyne DFC RCAF 263 Sqn Whirlwind pilot
"....always game I did a few flights on their Hurricane MkIV then had a go at their MKIX Spit again without the benefit of a handbook or even good advice. I took the Spit down to the gunnery range in the Channel and fired away , I was startled when the Spit went into a great skid . Immediately I stopped firing and pulled out from my dive realizing I had a cannon stoppage"

 

[Airframes]

Very interesting stuff! The answers from PB et al all fall in the category of 'correct'. There was, of course, another reason why the .303 inch round remained in R.A.F. service throughout WW2. Basically, as one person has mentioned, it had to do with stocks, and also manufacture and supply. This calibre of ammunition had been in (general) service since before WW1, and was manufactured not only in the U.K., but also in the (then) 'Colonies', particularly, and in very large quantities, in India. (it still is in the latter!) It should be remembered that, in the early stages of WW2, Britain was not in a position to cope with the changes required, on a massive scale, in order to change a 'standard' ammunition, used in a broad spectrum of weapons. These changes would not only effect the tooling-up of the factories, but also the logistics chain, spares and repairs, training, armourers tooling etc etc.
Also, apart from the accepted point that Britain had foresaw a (then) powerful weapon in an eight gun fighter (remember, the aircraft is just the means of getting the guns to the target, and the guns are only the delivery system for the real weapon, the bullet/shell), and adding this fact to the above, the British 'Powers that be' were slow, if not reluctant, to effect change. (To a point, they still are.) Even immediately after WW2, when the value of heavier armament, air and ground, was already known and accepted, it still took years to change. Then, plans were already mooted to change calibres of some weapons, in particular, infantry weapons and, in this case, the 'Powers' were already looking at a probable smaller calibre round, but with a high, or higher, velocity and power to weight ratio. Eventually, the British forces changed to what became the NATO standard, 7.62mm (.30 Cal) but that didn't happen until 1958! The current British infantry weapon (being generous with such a title!) the L85, more commonly called the SA80 (translated, heap of ****) stemmed from a 1947 design, the EM2, which had been originally designed around a short 7.62 round, but was also tested, and proven, with various smaller calibres. This weapon could have been in service long before the L1A1 SLR (licence built, semi-auto FN FAL), but, for want of a better term, was 'held back', for various 'political' reasons, and didn't actually go into full service until 1985! I had been involved in some of the field trials of earlier production-prototypes of this weapon as early as 1976!
So, apart from the logistics situation, and the massive stocks of .303 ammo, there was also the 'Establishment' to contend with. How we (Britain) ever achieved anything, considering the amount of b****y red tape (that still abounds) constricting things during WW2 will never cease to amaze me!
So, apologies for such a long winded response, and some (neccessary) digressions, but hopefully you will have understood what I mean! Basically, large stocks, dedicated calibre weapons, difficulty of change-over, logistics, and 1920's thinking in a World that was already, technologically, advancing faster in the five years of war than it had in the previous 100!

 

[Glider]

Very interesting stuff! The answers from PB et al all fall in the category of 'correct'. There was, of course, another reason why the .303 inch round remained in R.A.F. service throughout WW2. Basically, as one person has mentioned, it had to do with stocks, and also manufacture and supply. This calibre of ammunition had been in (general) service since before WW1, and was manufactured not only in the U.K., but also in the (then) 'Colonies', particularly, and in very large quantities, in India. (it still is in the latter!) It should be remembered that, in the early stages of WW2, Britain was not in a position to cope with the changes required, on a massive scale, in order to change a 'standard' ammunition, used in a broad spectrum of weapons. These changes would not only effect the tooling-up of the factories, but also the logistics chain, spares and repairs, training, armourers tooling etc etc.

This argument doesn't hold up when you remember that we were doing all these tasks to bring the 20mm into service.

Also, apart from the accepted point that Britain had foresaw a (then) powerful weapon in an eight gun fighter (remember, the aircraft is just the means of getting the guns to the target, and the guns are only the delivery system for the real weapon, the bullet/shell), and adding this fact to the above, the British 'Powers that be' were slow, if not reluctant, to effect change. (To a point, they still are.)

If we are discussing the aircraft weapons then this statement I would question. Despite having the 20mm Hispano V arguably the best 20mm of the war, the British didn't hesitate to develop the 30mm Aden when the US were still using the 0.50 M3.

Even immediately after WW2, when the value of heavier armament, air and ground, was already known and accepted, it still took years to change. Then, plans were already mooted to change calibres of some weapons, in particular, infantry weapons and, in this case, the 'Powers' were already looking at a probable smaller calibre round, but with a high, or higher, velocity and power to weight ratio. Eventually, the British forces changed to what became the NATO standard, 7.62mm (.30 Cal) but that didn't happen until 1958! The current British infantry weapon (being generous with such a title!) the L85, more commonly called the SA80 (translated, heap of ****) stemmed from a 1947 design, the EM2, which had been originally designed around a short 7.62 round, but was also tested, and proven, with various smaller calibres.
This weapon could have been in service long before the L1A1 SLR (licence built, semi-auto FN FAL), but, for want of a better term, was 'held back', for various 'political' reasons, and didn't actually go into full service until 1985! I had been involved in some of the field trials of earlier production-prototypes of this weapon as early as 1976!

Again I must question some of these points. The ground breaking EM2 was designed for a brand new .280 round which we wanted to use in Nato in 1948, indeed the EM" was chosen as the new Army rifle in 1951. This wasn't allowed because the USA wanted to stick with the 7.62.
So the British were keen to change the round, as were the Belgian FN Company who were impressed with it and started to develop their own weapons around it.
As for the SA80 there is no doubt it was a disaster when introduced but has developed into a reliable weapon.

 

[renrich]

I do remember the British favoring the 280 and somewhere I seem to remember them wanting to go to the 270(277) which I feel would have been a laudable choice. This may have been before WW2.