Kill Ratios

I know that some people are big fans of Kill Ratios, but I am not.
The reasons why I am not a fan are ;
1) the success rate of one aircraft is a product of a LOT of factors. Some of them are ; the quality of the opposing aircraft, their pilots, and the doctrine of their air force.
2) The situation in which the combat or ambush takes place. A defending/ intercepting force may be at a disadvantage of lack of numbers or altitude.
3) The experience of the pilots of both sides. During the BoB, the RAF used outdated tactics - VIC formation etc and had not had the experience that the LW gained in Spain, Poland etc. So in simple terms it was rookies against pro's. It is not that surprising then, that the LW fighters did quite well. Similarly, on the Eastern Front. the LW faced obsolete aircraft flown by inexperienced pilots. The same could be said about the Japanese forces in the Far East - they had experience as well as modern aircraft against some obsolete inexperienced opposition.
When the Allies gained experience and learned from their mistakes and adopted tactics better suited to their aircrafts relative strengths and exploiting their opponents weaknesses - the boot began to be put on the other foot. This is most obvious in the European Theatre when the RAF and USAAF changed tactics and allowed fighter aircraft to seek out the LW on the ground and in the air and also not be tied to close bomber escort. This quickly degrade the LW in terms of strength and also vitally in terms of experienced pilots. A similar situation late in the PTO saw the Japanese lose most of their experienced pilots and aircraft and become a shadow of its former self.
None of the above is taken into account in simple Kill Ratios.

The contribution of other systems/data inputs should not be understated. By 1940, the era of the "by chance" intercept, which had been the norm for the preceding 25+ years, was at an end. The Battle of Britain was a tactical success in large part because of non-aircraft factors like radar, ground control system and intelligence. Lack of such inputs put any defending force at a disadvantage. Conversely, correct use of such enterprise-level systems resulted in much improved performance by fighter aircraft (eg the Marianas Turkey Shoot).

The large majority of victories were scored when the victim was unaware that he was being attacked until bullets started hitting his aircraft. There is NO system that takes this into account. Dogfights happened, but ambush kills were much more frequent. That from the pilots who flew the war, many times over, over years of hearing it.

My own preferred indicator of pilot skill is victories divided by combat missions flown, with a combat mission being a mission on which enemy aircraft were engaged. This tells us nothing about the aircraft being flown, but is a fairly decent indicator of pilot skill. Unfortunately, even this measure is heavily influenced by the number of targets available to the missions being flown. The ETO was relatively target-rich, with a lot of planes being in the sky over Europe almost any day. The PTO was relatively target-poor, with the ocean being large, and the number of planes being almost laughably low compared with the ETO opportunities. Yet, the top two scorers from the U.S.A. came from the PTO.

Kill ratio is about the only measure of aircraft quality I can think of, and it has the same problem the measure above has ... where can you get the data?

Unfortunately, the data are very difficult to get for almost ANY system of measure. making these discussions interesting even 80 years after the fact. I bet it won't be settled, EVER, but the discussions are fun, aren't they?

Cheers.

Ref. the generic Wildcat v. FM-2 "Wilder Wildcat." A matter of different kittens in the litter. The FM-2 was similar weight to the F4F-4 (FM-1 was nearly identical) with more hosspower. While the six-gun dash four Wildcat (due to RN influence) delivered more rounds on target, it provided significantly less trigger time than the dash three, which had performed better because it was lighter. Similarly, the armament difference between B/C Mustangs and D models affected kill pecentages, somewhat. Would have to dig out my scratchings, but IIRC the 50% increase in firepower (6 guns v. 4) resulted in about 10% increase in claimed lethality. Short version: in WW II air combat, four .50s were optimum.

Barrett said:

Ref. the generic Wildcat v. FM-2 "Wilder Wildcat." A matter of different kittens in the litter. The FM-2 was similar weight to the F4F-4 (FM-1 was nearly identical) with more hosspower. While the six-gun dash four Wildcat (due to RN influence) delivered more rounds on target, it provided significantly less trigger time than the dash three, which had performed better because it was lighter. Similarly, the armament difference between B/C Mustangs and D models affected kill pecentages, somewhat. Would have to dig out my scratchings, but IIRC the 50% increase in firepower (6 guns v. 4) resulted in about 10% increase in claimed lethality. Short version: in WW II air combat, four .50s were optimum.

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I think that what is optimum depends on how many P51-Ds ran out of ammunition, a 10% increase in anything is actually huge.

According to the Germans, the undoubted masters at fighter combat, one gun in the fuselage was worth two in the wings because they were all aimed straight with no convergence to disrupt the pattern after the point o convergence.

So, I'd really love to see some hard data that either confirm or give that claim the boot. The Bf 109 had fuselage guns throughout all it's life and was a VERY good killer of airplanes. I'd say that pretty well confirms it. Also, the U.S. mount of the top two aces was the P-38, with all fuselage guns. But the Hellcat and P-51 were quite good, too.

I'm thinking the best armament was a combination of cannons and MG, selectable by the pilot, that allowed the pilot to choose hitting power or rate of fire or both, depending on circumstances ... or else four 20 mm cannons and hang the MGs.

It tells me a lot that virtually all fighters went to cannons after Korea, but tells me nothing about what was optimum with the power and guns available in WWII. I'm leaning toward cannons, myself. This brings back shades of the old "great fighter gun debate."

See: The WWII Fighter Gun Debate: Gun Tables

I hope we don't contrive to re-post that all again but, if so, at least we have some good copy to read going forward.

Not exactly conclusive but the top three planes in order of kills against the V1 were cannon armed. While the Tempest was the quickest at low altitude the Mosquito certainly wasn't.

My view has always been that in WWII cannon armament proved to be more lethal on bigger slower moving targets such as bombers, but on the smaller faster and more maneuverable fighters nor so much. With a cannon's inherently lower muzzle velocity and fewer rounds available per gun on average, a pilot may find more comfort with a couple of extra .50 cal. or 12.7mm in fighter vs fighter combat where he has a better chance of getting hits on target. Does anyone have any statistics concerning the overall effectiveness of cannons vs machine guns in WWII fighter vs fighter combat? I have no problem being educated to believe otherwise...

DarrenW said:

My view has always been that in WWII cannon armament proved to be more lethal on bigger slower moving targets such as bombers, but on the smaller faster and more maneuverable fighters nor so much. With a cannon's inherently lower muzzle velocity and fewer rounds available per gun on average, a pilot may find more comfort with a couple of extra .50 cal. or 12.7mm in fighter vs fighter combat where he has a better chance of getting hits on target. Does anyone have any statistics concerning the overall effectiveness of cannons vs machine guns in WWII fighter vs fighter combat? I have no problem being educated to believe otherwise...

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In what seems like a simple question there is a lot of politics and logistics too. An organisation with thousands of machines prefers those machines to use the same equipment, once a few million rounds of ammunition have been ordered and stockpiled they become a big argument for continued use, at least until they are used up. You cannot compare a gun with any other gun, it is a system as loaded onto an aircraft. The rifle calibre MGs at their best with a combination of incendiary and AP rounds were much more effective than cannon rounds at their worst which failed to explode. In any case there is always the problem of weight, a Spitfire couldn't carry 8 cannon but did carry 8 x 0.303 mgs it is therefore a comparison of weight of fire and overall effectiveness.

The RAF set 4 x 20mm cannon as their standard armament sometime in 1940/41, all fighters had this except its most successful one, the Spitfire. The Spitfire's wings meant that the outer pair couldn't be properly heated, so 4 x .303 or 2 x 0.5 mgs were used in the outer wings. I learned here recently that Spitfires flew from Malta with 4 x 20mm cannon and also 4 x 0,303 mgs but that is a special case Hurricane Mk II, Typhoon, Tempest and Mustangs (P51s ordered by the British) as well as Whirlwind Beaufighter and Mosquito heavy fighters all had 4 x 20mm cannon specified. The RAF always had to consider attacks on UK which may have included larger slow moving targets.

pbehn said:

o 4 x .303 or 2 x 0.5 mgs were used in the outer wings.

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When Spits were equipped with the Browning .50 HMGs they were fitted in the inner gun position.
Concise Guide To Spitfire Wing Types — Variants & Technology | Reference

DarrenW said:

My view has always been that in WWII cannon armament proved to be more lethal on bigger slower moving targets such as bombers, but on the smaller faster and more maneuverable fighters nor so much. With a cannon's inherently lower muzzle velocity and fewer rounds available per gun on average, a pilot may find more comfort with a couple of extra .50 cal. or 12.7mm in fighter vs fighter combat where he has a better chance of getting hits on target. Does anyone have any statistics concerning the overall effectiveness of cannons vs machine guns in WWII fighter vs fighter combat? I have no problem being educated to believe otherwise...

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Unfortunate the guns themselves (and guns includes ammo) preclude such a simple statement. The German 13mm was the lowest powered 'heavy' machine gun used in WW II with a light, for it's size, bullet and the lowest velocity. A German pilot with six such guns and no cannon would not have been much better off. Since the gun was designed for cowl mounting to replace the older 7.9mm MG 17 this should not be taken as a failure as it did increase a fighters punch over the 7.9mm guns (it was also the lightest 'heavy' machine gun).

AS the discussion in the other thread shows, 20mm guns showed a huge variation in shell weight, muzzle velocity and rate of fire.
For the allies the only 20mm gun that matters is the 20mm Hispano and the only .50 cal/12.7mm is the Browning .50 cal. There has been a crap load a of internet band width and a crap load of ink and paper used comparing these.

Boiling it down the 20mm Hispano, for most of the war, fired at about 600rpm or 10 rounds per second so firing time is pretty easy to figure out. About the only allied fighters built in quantity to use the 60 round drums were the first 400 Beaufighters, the Spitfire Vb and some P-39 Aircobras. Just about everything else got belts of various sizes/lengths. Basically 12-20 seconds of firing time for the belt fed Hispanos. how much is enough? The Browning fired at about 800rpm in the version most often used during the war or about 13 rounds per second (or 13 and a fraction). You really need the extra pair of guns to get a significantly higher rate of fire.

as for "cannon's inherently lower muzzle velocity" this is most emphatically not the case in regards to the Hispano and the Browning .50cal.
The Hispano had a MV of about 860metes/sec while the .50 had one of of 890m/s at best. Please be sure you are comparing the right barrels as often the velocity for the.50 is given from 45in ground barrels and not the 36in barrels used in aircraft. There was also a variation in types of projectiles.
The 20mm Hispano and the .50 cal and very similar trajectories and times of flight out 600yds and beyond making any practical differences in air to air combat irrelevant. Not so against other 20mm so........

US Navy figured that one 20mm was worth three .50 cal so a plane with 4 four 20mm Hispano's was worth ?????????

Barring golden BBs the 20mm shells were much more destructive. Here the US really had a problem as they never used a HE projectile from the .50 and went to a hybrid armor piercing incendiary round for the majority of their ammo. The AP core meant that only about 1 gram of incendiary material per bullet was carried (a bit under what a British .303 incendiary carried) and the incendiary material was carried in the nose ahead of the AP core so it would be stripped away on any substantial structure hit and not carried into the aircraft interior.

you need to make more hits with the .50 to cause equal damage.

I would note that the US Navy, which was not happy with 6 gun Wildcats armed with 240rpg in 1942, was experimenting with Corsairs armed with four 20mm guns and F6Fs with the inner most .50 replaced by a 20mm gun in 1944 and in fact the US Navy never ordered a plane armed with .50 cal guns after Dec of 1944 (took delivery of plenty) but the FH-1 Phantom jet was the last NEW design to be ordered using .50 cal guns.

I would note that both higher rate of fire .50 cal guns and high velocity, high capacity .50 cal incendiary ammo were well in the works when the Navy made these decisions.

What conclusions can you draw from this?

DarrenW said:

My view has always been that in WWII cannon armament proved to be more lethal on bigger slower moving targets such as bombers, but on the smaller faster and more maneuverable fighters nor so much. With a cannon's inherently lower muzzle velocity and fewer rounds available per gun on average, a pilot may find more comfort with a couple of extra .50 cal. or 12.7mm in fighter vs fighter combat where he has a better chance of getting hits on target.

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There was plenty of cannons with high muzzle velocity in ww2 - MK 151/15, VJa-23, NS-37, MK 103 (granted, this is a bit of stretch for ww2 A-to-A fight), Hispano as noted by Shortround6, some Japanese cannons. In the same time there was plenty of ~.50 MGs witl low MV, like Italian or German types.

Does anyone have any statistics concerning the overall effectiveness of cannons vs machine guns in WWII fighter vs fighter combat? I have no problem being educated to believe otherwise...

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Soviets made a comparison between the results of firepower of Yak-3 (2 HMGs, 1 cannon) and La-7 (two synchronised cannons) with regard to downing anything the Germans threw at them from ~mid 1944 until VE day (read mostly fighters or fighter-bombers). Yak-3 ended emerged as a winner vs. La-7.
I'll try to find the comparison.

Here it is: link.
A very good read.

And we have one end of the spectrum. The Russian 12.7mm was the most powerful 12.7mm and the Russian 20mm used the 2nd smallest (lightest) conventional shell. The Russian 20mm being essentially a necked up 12.7mm cartridge case.

I like this part
"Comment for the last table: we must bear in mind that the objectives for the Yak-3 and La-7 (1944-45) were in many cases the FW-190, that is, the well-armored aircraft, and the UBS machine guns. better drilling compared to ShVAK guns"

I am interpreting the bolded part as "better penetration" but could be wrong

The 20mm ShVAK ammo used projectiles of 91-99 grams and seem to be a little sensitive to weight and velocity. The light shells having a MV of 790m/s and the slightly heavier ones dropping to 770 or 750m/s. There were AP projectiles but these had little (2.5 grams incendiary) or no HE/incendiary filler.

The 12.7 Russian used perhaps 10 different projectiles in WW II and four of them were HE or HEI, Leaving out the tungsten cored projectile the regular 12.7mm AP had good penetration while the short, squaty 20mm projectiles did not.
A 12.7mm projectile is trying to make a hole about 40% of the size of the hole a 20mm projectile is making so high powered 12.7mm guns can often exceed the penetration of low powered 20mm rounds.

For Details see. From 20mm to 25mm - The Russian Ammunition Page
and From 12.7mm to 14.5mm - The Russian Ammunition Page

The Russian 20mm HE ammo never exceeding 6.7 grams of HE and more commonly 2.8 grams HE + 3.3 grams incendiary.

British 20mm Hispano HE carried 10.2/10.5 grams HE and US HEI carried 7 grams HE and 4.3 grams incendiary. Obviously 128-130 gram shells do more damage than 91-99 gram shells.

Thanks for sharing your abundant knowledge on this subject pbehn, fastmongrel, Tomo, and Shortround6. It would seem that I have much to learn about WWII aircraft weaponry but something tells me that I came to the right place to accomplish just that.

DarrenW said:

Thanks for sharing your abundant knowledge on this subject pbehn, fastmongrel, Tomo, and Shortround6. It would seem that I have much to learn about WWII aircraft weaponry but something tells me that I came to the right place to accomplish just that.

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Hey, don't include me in your list, 90% of what I know I read on here

pbehn said:

Hey, don't include me in your list, 90% of what I know I read on here

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You get the bacon for your honesty Sir!

DarrenW said:

You get the bacon for your honesty Sir!

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There is also, as there always is a time element. The British in 1940 were faced with increasingly heavily protected bombers and fighters, the British had new bomber designs coming into production so it is a normal assumption that the Germans did too. If in 1936-39 the Brits had the option of a reliable 0.5 cal MG they may have taken it but really it wasn't there, at the time. Once committed to a system it has its own inertia and momentum, there were many mods to the British 0.303 MGs to make the best of a bad job until the cannons were got to being a serviceable weapon. The Spitfire was originally specified with 4 x 0.303 MGs and ended being specified with 4 x 20mm cannon. That is not only a statement of what was needed but also what was possible. A Spitfire Mk 1 with 4 cannon may have been devastating in 1940 taking on the LW bombers, if it managed to get up high enough in time to do anything other than give a wave goodbye, at the time they had a lot of trouble just getting 2 to work.

Was reading something that referenced a VIII Fighter Command (P-47) study that said the average duration of fire for a successful attack vs. a Ju88 was 15 seconds.

Things that came to mind:

• it's doubtful the Spitfire was ever going to carry 8 x .5in Brownings (probably 4)
• it's doubtful the Spitfire was ever going to carry as much .5-inch ammo in total as the P47 could fire in 15 seconds
• the P-47 is probably a better gun platform than the Spitfire
• while the toughest to actually catch, the Ju88 seems to be the most vulnerable of the three main German types

I think the Hispano was the right call.