CANNON OR MACHINE GUN? Pt. 1

Discussion in 'Aviation' started by syscom3, Apr 7, 2006.

  1. syscom3

    syscom3 Pacific Historian

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    I received this in an e-mail today.

    CANNON OR MACHINE GUN? The Second World War Aircraft Gun Controversy

    Anthony G Williams

    This article first appeared in Aeroplane Magazine in
    September 2004. It is based on material in

    Flying Guns – World War 2: Development of Aircraft
    Guns, Ammunition and Installations 1933-45



    The Second World War stimulated an important advance
    in aircraft gun armament. The fighters of most
    combatant nations began the war with a few
    rifle*calibre machine-guns (RCMGs) of 7.5-8 mm
    calibre, but, by the end of the conflict, cannon of 20
    mm or greater calibre were standard. The one exception
    was the USA, which relied overwhelmingly on the 12.7
    mm (0.50 inch) M2 Browning heavy machine-gun (HMG).
    Students of armament history continue to argue: why
    did this happen, and were the Americans right?



    EARLY FIGHTING

    In 1939 the RAF's new Spitfire and Hurricane fighters
    were remarkable for their heavy battery of eight
    wing-mounted 0.303 inch (7.7 mm) RCMGs; twice as
    powerful as that of any other major fighter. In
    contrast, Germany's Luftwaffe had been watching the
    French use of engine-mounted cannon. In 1932 this
    resulted in a requirement for a fighter with two RCMGs
    or a single 20 mm cannon. The weapon considered was
    the large, very powerful but slow-firing
    Rheinmetall*Borsig MG C/30L, firing through the
    propeller hub. An initial experiment with a prototype
    Heinkel He 112 in the Spanish Civil War showed that
    this installation was unsatisfactory for aerial
    combat, though effective in ground attack.

    Germany then went to the opposite extreme and selected
    the small, low-velocity Swiss Oerlikon FF 20 mm cannon
    for development. A modified version, the MG-FF, was
    put into pro*duction by Ikaria Werke Berlin, and
    entered Luftwaffe service. Initial attempts to fit
    this as an engine gun ran into reliability problems,
    so the Messerschmitt Bf 109E-3 of 1939 carried two
    MG-FFs in the wings and a pair of 7.92 mm MG 17 guns
    synchronised to fire through the propeller disc.
    However, many Bf 109s were still armed with four RCMGs
    at the start of the war.

    The Battle of France caught the French with few
    fighters capable of dealing with the Bf 109s. Most
    French fighters carried a mixture of 20 mm cannon and
    RCMGs; the best was the Dewoitine D.520 with its four
    wing-mounted 7.5 mm MAC34 M39 MGs and the powerful,
    fast-firing Hispano-Suiza HS 404 moteur canon. The
    US-*built Curtiss Hawk H-75A, with four or six 7.5 mm
    FN-Browning guns, was too lightly armed.

    One lesson of early fighting was that the RAF
    fighters' battery of RCMGs was less effective than
    expected. Although the eight guns between them fired
    no fewer than 160 rounds per second (rps), they were
    initially adjusted to concentrate their fire at the
    long range of 365 m which led to the bullet strikes
    being spread across the target at shorter ranges. As
    self-sealing fuel tanks and armour became much more
    common during 1940, it proved necessary to concentrate
    fire at much closer ranges.

    The problem was that the small bullets fired by the
    RCMGs could not carry enough incendiary or explosive
    to guarantee success, and also had insufficient
    penetration to defeat armour reliably. A series of
    ground tests carried out by the British, firing at a
    redundant Bristol Blenheim from 180 m to the rear with
    various British and German guns and ammunition,
    revealed that the .303 incendiary B Mk VI bullets
    would set light to a Blenheim wing tank with only one
    hit in five; during the Battle only one or two of the
    eight guns were normally loaded with this ammunition.
    Other .303 and 7.92 mm incendiaries were only half as
    effective. Similarly, while both German and British
    steel-cored armour-piercing (AP) rounds could
    penetrate up to 12 mm of armour plate if fired
    directly at it from 180 m, most of the bullets were
    deflected or tumbled by first passing through the
    fuselage skin or structure. In consequence, only a
    quarter to a third of the bullets reached the
    Blenheim's 4 mm-thick armour plate at all, and very
    few penetrated it.

    The Luftwaffe relied more on their 20 mm MG*FF cannon,
    which had some interesting advantages and
    disadvantages. The guns were more than twice as heavy
    as the 7.92 mm MG 17 and fired only half as fast, at
    about 9 rps. The muzzle velocity was also lower,
    giving a different trajectory and time-to-target.
    Moreover, the 60*round capacity of its drum magazine
    limited the weapon to only about 7 secs of firing.
    However, the big shells weighed about 12 times as much
    as the RCMG bullets, and their high-explosive filling
    caused blast damage, as well as throwing high-velocity
    shell fragments around.

    In May 1940 the Bf 109E-4 entered service with the
    modified MG-FFM gun, adapted to fire the new
    Minengeschoss (mine shell) ammunition which had very
    thin walls and a doubled capacity for high explosive
    (HE) and/or incendiary. As a bonus the shells were
    lighter, permitting a higher muzzle velocity. The
    theory was that solid bullets or AP cannon shells
    relied on hitting the relatively small vital areas to
    have an effect, whereas an HE shell could cause
    serious damage regardless of where it struck. There is
    no doubt that this theory was correct: the Spitfires
    and Hurricanes would have had far more effect on the
    Luftwaffe's bombers had they been armed with four
    MG-FFM cannon, which would have weighed little more
    than their battery of RCMGs..
     
  2. syscom3

    syscom3 Pacific Historian

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    CANNON OR MACHINE GUN? The Second World War Aircraft Gun Controversy

    Anthony G Williams

    This article first appeared in Aeroplane Magazine in
    September 2004. It is based on material in

    Flying Guns – World War 2: Development of Aircraft
    Guns, Ammunition and Installations 1933-45
    THE SEARCH FOR BIGGER GUNS

    The RAF had realised years before the war that the
    .303 MG might become inadequate as a primary aircraft
    gun, given the steady increase in speed, strength and
    toughness of aircraft. They considered, but rejected,
    .50 inch (I2.7 mm) guns as giving insufficient
    advantage over the .303. Instead, they sought a good
    20 mm cannon, which they thought would be far more
    effective due to its explosive ammunition, and found
    one in the new French Hispano-Suiza HS.404. This was
    selected in the late 1930s, and specifications were
    written for a new fighter to carry it (the Westland
    Whirlwind), but problems in setting up UK factories
    meant that only a few guns were available for the
    Battle of Britain.

    To save time the Hispano was fitted to existing
    single-engined fighters for testing, and a squadron of
    Spitfire IBs saw service during the Battle. However,
    the gun was designed to be mounted on a massive engine
    block, and did not like being installed in a far more
    flexible wing. Moreover, the initial installation had
    the guns on their sides to bury the big drum magazines
    in the wings, and the Hispano did not like this at
    all. The result was such appalling unreliability, the
    guns frequently jamming after only one shot, that the
    squadron requested its old aeroplanes back.

    Throughout the Hispano's life, fine-tuning of
    installations was required to make it reliable in wing
    mountings. Guns mounted in the much more rigid
    fuselages of such aircraft as the Whirlwind,
    Beaufighter and Mosquito caused far fewer problems.
    Once working properly, the big cannon was a formidable
    weapon. Compared with the MG-FF it was slightly
    faster-firing at 10 rps, and its much bigger cartridge
    cases generated a considerably higher muzzle velocity,
    which improved both hit probability and penetration.
    While the Allies never introduced the Minengeschoss
    technology, so their shells only carried half the
    HE/Incendiary (HEI) load, the heavy Hispano shells'
    better penetration meant they could inflict
    considerable damage. The Hispano soon changed from a
    60-round drum magazine to a belt feed giving much
    greater ammunition capacity (which the MG-FF never
    had, other than in an obscure nightfighter
    installation). The penalty was that the Hispano was
    almost twice as long as and double the weight of the
    German gun; unwelcome features for wing-mounted
    weapons.

    RAF fighters carried a mixture of HE or HEI and plain
    steel "ball" (practice) rounds (which had good
    penetration) until the emergence of the semi-armour
    piercing incendiary (SAPI) in 1942, after which the
    standard loading was 50/50 HEI and SAPI. The German
    cannon were not exclusively loaded with Minengeschoss,
    but used them mixed with older-type HEI-T shells
    (retained because, unlike the M-Geschoss, they could
    carry a tracer) and later some API rounds as well, in
    varying proportions.

    The Germans were not satisfied with the MG-FFM, which
    had been adopted as an interim measure pending the
    development of a purpose-designed cannon. This duly
    emerged as the Mauser MG 151, which gradually took
    over from 1941. Initially, the Mauser had been
    designed to use a high-velocity 15 mm cartridge, but
    it saw relatively little service in this form. Wartime
    experience led to the cartridge case being modified to
    accept the 20 mm shells from the MG-FFM, surrendering
    muzzle velocity and penetration in the interests of
    far greater destructive effect. The 15 mm version was
    available with HE shells, but they were considered too
    small. The resulting MG 151/20 was intermediate in
    size, weight and muzzle velocity between the MG-FFM
    and the Hispano, but was faster-firing at 12 rps. It
    was a superb design which the Americans tried to copy,
    producing some 300 guns in .60 inch (15.2 mm) calibre,
    designated T17, but they never adopted it.

    Later in the war, various new German guns emerged with
    calibres of up to 50 mm. The most significant ones
    were the Rheinmetall-Borsig MG 131, MK 103 and MK 108.
    The MG 131 was a 13 mm HMG intended to replace the
    RCMGs in both fixed and movable mountings, and
    therefore kept as small and light as possible, making
    it the least powerful HMG to see service. The other
    guns were both in 30 mm calibre but otherwise very
    different. The MK 103 was a huge, high-velocity
    slow-firing gun, while the MK 108 fired much smaller,
    low-velocity cartridges at a very creditable 10 rps,
    and was only half the size and weight. Their use was
    really prompted by the difficulty the Luftwaffe was
    experiencing in shooting down USAAF B-17 bombers.
    Their 30 mm M-Geschoss HEI shells were highly
    effective, containing four times as much HE as the 20
    mm version, and three or four hits with these could
    bring down a bomber, compared with 20 hits with 20 mm
    ammunition.

    In 1941 the USSR was attacked by Germany and thereby
    drawn into the wider conflict. As well as the
    very-fast-firing (30 rps) 7.62 mm ShKAS, it had in
    service an excellent HMG, the 12.7 mm Universal
    Berezin, and a 20 mm cannon, the ShVAK. The ShVAK had
    actually started life as a 12.7 mm gun. It weighed the
    same as the MG 151/20 and was slightly faster-firing,
    but the ammunition was less effective as the shells
    had only a small HE capacity. Towards the end of the
    war the Berezin was also altered to fire the same 20
    mm ammunition as the ShVAK; at 25 kg the resulting
    B-20 was the lightest gun of this calibre to see
    service. The Soviet preference was to install all guns
    in the fuselage of their little fighters rather than
    in the wings, to concentrate firepower and make the
    aircraft more agile. Because this limited the number
    of guns, a relatively small number of aircraft was
    equipped with larger guns as engine cannon, including
    the powerful 23 mm VYa-23 and 37 mm NS-37. Because of
    the weight, recoil and relatively low rate of fire of
    these weapons, these were deemed suitable for expert
    pilots only.
     
  3. syscom3

    syscom3 Pacific Historian

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    CANNON OR MACHINE GUN? The Second World War Aircraft Gun Controversy

    Anthony G Williams

    This article first appeared in Aeroplane Magazine in
    September 2004. It is based on material in

    Flying Guns – World War 2: Development of Aircraft
    Guns, Ammunition and Installations 1933-45

    ENTER THE AMERICANS - AND THE JAPANESE

    The end of 1941 also saw America and Japan enter the
    war. Their aircraft weapons were very different.
    America relied almost entirely on the Browning
    machine-gun, not just in .50 (12.7 mm) calibre, but,
    for the first couple of years, in .30 (7.62mm) as
    well. The Japanese army and navy air forces followed
    their own paths, the army steadily up-gunning from 7.7
    mm through 12.7 mm machine-guns and later 20 mm
    cannon, with 30 mm and even larger guns seeing limited
    service by the end of the war. The navy started with a
    mixture of 7.7mm MGs and Type 99 (Oerlikon) 20 mm
    cannon and continued to rely on this cannon (initially
    the low-velocity Type 99-1, later the more powerful
    Type 99-2), although it did make some use of HMGs and
    was also introducing 30 mm guns by the end of the war.
    As in Germany, the destruction of American heavy
    bombers was a strong incentive for the development of
    weapons of 30 mm or larger calibre.

    The Americans did not intend to make such a commitment
    to the Browning MGs. Both before and during the war
    considerable efforts were made to secure alternative
    aircraft guns. Trials of foreign equipment resulted in
    the selection of the 20 mm Hispano-Suiza HS 404, large
    numbers being made. The Browning-designed 37 mm M4
    cannon was also introduced, although used almost
    exclusively by the Bell P-39 and P-63. However, the
    standard fighter armament became a battery of six .50
    inch Browning M2 HMGs.

    This has led to the often-expressed view that the .50
    inch M2 was the best all-round fighter gun of the war.
    After all, the USAAF and US Navy fighters
    unquestionably came to dominate the skies in which
    they fought. If there had been a better gun, America
    would have used it. However, the truth is not quite as
    simple as that. There are two issues here; how good
    was the .50 M2 compared with other HMGs, and how
    effective was it compared with cannon?

    The most obvious comparator was the Soviet UB, which
    fired ammunition of virtually identical power. The UB
    weighed 25 kg, compared with the M2's 29 kg, but the
    Soviet gun fired at 17.5 rps, compared with around 13
    for the M2. In terms of power- to-weight ratio the
    Berezin was therefore clearly superior. The Browning
    fared better against most other HMGs, as they all
    fired less-powerful ammunition, so the M2 enjoyed
    advantages in range and penetration. However, it had a
    slightly lower rate of fire than the German and
    Japanese guns (both around 15 rps), and was also
    bigger and heavier. The most powerful of all of the
    HMGs was the 15 mm MG 151, but this was heavier and
    slower-firing than the M2. Overall, therefore, the .50
    M2 was not the best of the HMGs but was about average,
    with reasonable performance for its weight.

    How did HMGs compare with 20 mm cannon? The first
    problem is that the cannon varied hugely in size,
    weight and performance. The MG*FFM, Type 99-1 and B-20
    were all lighter than the M2, but the first two were
    significantly worse in terms of muzzle velocity and
    rate of fire, although the B-20 matched the M2's rate
    of fire and was not far behind in velocity. The
    Japanese Ho-5 and Type 99-2 and the ShVAK and MG
    151/20 were all somewhat heavier. Muzzle velocities
    and rates of fire were closer to the M2's but
    generally still not as good. The Hispano was
    significantly heavier and slower-firing until the
    British Mk V emerged near the war's end, matching the
    MG 151/20 in weight and rate of fire.

    The foregoing compares only the guns' efficiency; it
    takes no account of ammunition, the area in which the
    HMG loses most ground. The 20 mm cannon shells were
    not only two to three times heavier than HMG bullets,
    but their HEI contents greatly increased their
    effectiveness. Although HE ammunition was available
    for most HMGs, their small bullets severely limited
    the quantity of chemicals carried, so the Americans
    decided not to use them. Initially, the M2 used a mix
    of incendiary and AP bullets, with some tracers, but
    in 1944 the M8 API began to take over. Rather
    curiously, this was based on the Soviet B.32 API used
    in the Berezin.

    It is difficult to assess the effectiveness of
    different ammunition types, but various tests suggest
    that a typical World War Two-era HE or incendiary
    shell, with chemical contents forming about 10 per
    cent of total shell weight, was about twice as
    destructive as a plain steel shell of similar size and
    weight. This makes it clear that 20 mm cannon were
    considerably more destructive for a given total weight
    of armament than any HMG could hope to be. For
    example, the .50 M8 API contained less than one gram
    of incendiary, whereas the 20 mm Hispano SAPI achieved
    similar armour penetration but carried more than ten
    times as much incendiary material.

    This advantage was recognised by the US Navy. After
    comparing the .50 M2 and the 20 mm Hispano they
    estimated that the cannon was three times as
    effective. In other words, the typical RAF armament of
    four 20 mm cannon was twice as destructive as the
    USAAF's six .50 HMGs, for very little more weight.
    Proponents of the Browning HMG point to its excellent
    ballistics, which enhanced its range and hit
    probability. But the Hispano's muzzle velocity was
    very similar, and although the blunt-nosed shells were
    less aerodynamic the difference over typical
    air-combat ranges was not significant.

    The cannon's advantages are clearly shown in the
    decisions made as a result of combat experience by air
    forces with a choice of good HMGs and cannon. We have
    already seen how Germany preferred the 20 mm version
    of the MG 151 despite its poorer ballistics. In the
    12.7 mm Berezin the Soviets had arguably the best HMG
    of the war, but they still preferred the heavier,
    slower-firing 20 mm ShVAK. Japan had several good HMGs
    available; the army's Ho-103, and the navy's 13 mm
    Type 3, a .50 Browning chambered for slightly
    larger-calibre ammunition, but they made increasing
    use of cannon.

    So why did the Americans not make more use of cannon,
    specifically the 20 mm Hispano they already had in
    mass production? There were two main reasons. One was
    certainly that the M2 was adequate for its purpose. In
    Western Europe the main adversaries were fighters,
    which were much easier to damage and shoot down than
    bombers. In the Pacific Theatre the Japanese aircraft
    were initially poorly protected and easy to shoot
    down. Later Japanese aircraft were better protected,
    but again these were usually fighters. If the
    Americans had faced the need to stop raids by heavy,
    well-protected bombers, it is likely that the HMG's
    shortcomings would have been starkly revealed.

    There was another reason, however, which explains why
    the US Navy, despite rating the cannon very highly and
    facing the need to deal with attacking bombers and
    kamikazes, fitted it to few aircraft. That was serious
    production prob*lems with the American Hispano, which
    gave it a reputation for unreliability. Despite
    production running well into six figures, the American
    Hispano failed to achieve an acceptable reliability
    standard for the duration of the war.

    To return to the original question, were the Americans
    right to rely so heavily on the .50 M2 when all other
    combatant nations had a clear preference for cannon of
    at least 20 mm calibre? The answer has to be yes. It
    was adequate for its purpose, and was the only
    satisfactory aircraft gun in production in the USA. It
    was very reliable (except where the installations
    created problems), was made in huge quantities, and
    the simplification of supply by comparison with the
    diversity of weapons used by the Axis powers gave a
    major logistical advantage. However, the Americans
    could get away with using a weapon so deficient in
    destructive power not only because of the nature of
    their opposition, but also because the size and engine
    power of their fighters enabled them to carry a
    battery of at least six guns, thus making up in
    quantity what they lacked in destructive quality.

    The advantages of the 20 mm Hispano M2 were not
    entirely ignored. It was carried by Lockheed P-38s,
    together with four .50 Brownings. It was also
    installed in nightfighters, which needed maximum
    firepower to convert a short firing opportunity into a
    kill. Four were installed in Northrop's P-61 Black
    Widow, and two could be mounted in a Grumman F6F-5N.
    The cannon's extra firepower was also appreciated for
    ground strafing.

    After the war the US Navy quickly changed over to the
    20 mm cannon in its improved, faster-firing and more
    reliable M3 form, but the USAF stayed with the .50 M3
    until the fighting in Korea demonstrated once and for
    all that the HMG had had its day. From the mid-1950s
    the USAF at last replaced the old Browning with 20 mm
    cannon, initially the M39 revolver and then the M61
    rotary - just as most of the rest of the world was
    moving up to 30 mm!
     
  4. Glider

    Glider Well-Known Member

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    This is a good article that I first read in the magazine in question and saved. Its also a good summary of the history re the develoment of aircraft borne weapons
     
  5. lesofprimus

    lesofprimus Active Member

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    Yes it is, good read...
     
  6. Hot Space

    Hot Space Active Member

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    Yeah, cool that m8 :)

    I would go with a bit of both - 20mm .50's ;)
     
  7. Gnomey

    Gnomey World Travelling Doctor
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    Good interesting read syscom.
     
  8. Twitch

    Twitch Member

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    Setting aside idiosyncrocies of brands of weapons within the same caliber the 20 mm round should have been the acknowledged all around most usefull. The caliber itself seems best suited to the demands of the job in mid to late WW2. While we look at 30 mm types and conclude they are almost specialized in nature as they were mounted on machines in all countries whose role was anti-heavy bomber. On the other end of the spectrum the .30 caliber was about useless except in the very early stages of the war and then mostly in the hands of virtuoso shooters. Those with thirty caliber weapons mostly used them for ranging in their heavier cannon only.

    One of the problems with 20 mm magazines was simply that they held too few rounds. 60-100 rounds might have been ample for Saburo Sakai or Adolf Galland who were the products of the cream of the elite best pilots. For the pliots who weren't trained for extended periods due to the need for them to appear in action, it was woefully inadequate.

    The .50 caliber weapon of any manufacture had a tradeoff that lessened punch but retained fire time. Frankly it didn't matter if a "good" grade pilot took 700 rounds to bring down an enemy with fifties where an elite pilot used 70 rounds of 20 mms. The good pilot had ample ammo for a couple kills in the magazines even at that poor strike rate. Until much later with somewhat larger mags, 20 mms could not be spread around liberally in the air by trigger-happy pilots.

    In later .50s, and 20s ROF was about the same- 740 RPM. The math is easy. You got 200 20mms or 400 .50s. No the 20mm doesn't have exactly twice the killing power to make up for it. It's pretty close but weight and size restrictions make compromise necessary depending on the plane and the ordnance used if we diverge into that area beyond simple caliber cross section alone. All 20 mms are not equal. 12.7/.50s have more parody of universal application.

    It's one thing to easily stick a quartet of 20 mm Hispanos inside a Tempest's wing and quite another to get four MG 151s in a Bf 109's. Even if it were possible what about room for ammo?

    The pre and early war rifle caliber mentality for aerial weaponry was a throwback to WW I as was the bolt action arm for soldiers- inadequate for the modern combat that was about to unfold.

    The contention of low velocity of early 20 mm weapons is superfluous since the pilots knew their weapons and compensated to whatever degree was necessary. Any halfway sharp aerial gunman could alternate between high and lower velocity weapons by selecting their different triggers then mentally and physically compensate lead, drop and deflection. This was primary stuff. We idiot savants who know all the statistics of all the planes and weapons haven't got a clue to aerial gunnery beyond flight sims.

    .50 calibers were acceptable but becoming inadequate by late 1944 were as 20 mms had improved in velocity to the point of being the ideal caliber for times. Even so few planes carried a lot of rounds per gun. 20s should be considered the prime caliber of the aerial war as most effective I believe.
     
  9. R988

    R988 Member

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  10. syscom3

    syscom3 Pacific Historian

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    When it came to strafing, .50's were in some instances more effective than 20mm.

    .50's were just as deadly as 20mm against thin skinned vehicles. Plus, when you need to "hose down" an area with no specific target readily seen, the more lead you have flying around, the higher the probablity you will hit something.
     
  11. Jabberwocky

    Jabberwocky Active Member

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    I agree with your general thrust, but have to disagree on some specifics.


    Most 20mm armed fighters actually had between 120 and 150 rpg, some upwards of 200 rpg.

    Just looking at the ammunition for single engined fighter with 20mms and their firing time

    Spitfire Vb: 60 rpg (6 sec)
    Spitfire Vc: 120 rpg (12 sec)
    Spitfire IXe: 140 rpg (14 sec)
    Spitfire XXI: 150 rpg (15 sec)
    Hurricane IIc: 96 rpg (9 1/2 sec)
    Typhoon: 140 rpg (14 sec)
    Tempest: 200 rpg (16 sec)
    Firefly: 160 rpg (16 sec)
    109F/G: 150 rpg (12 1/2 sec)
    190A3-5: inner 200 rpg ( 16 1/2sec)
    outer 55 rpg ( 7 sec)
    190A6-9: inner 250 rpg ( 21 sec)
    outer 140 rpg ( 12 sec)
    A6M1-3: 60 rpg (7 1/2 sec)
    A6M5-8: 100 rpg (12 1/2 sec)
    Ki-61: 120 rpg ( 8 1/2 sec)
    Ki-100: 120 rpg ( 8 1/2 sec)
    Ki-84: 150 rpg (12 1/2 sec)
    N1K2-J: inner 230 rpg (17 1/2 sec)
    outer 150 rpg (11 1/2 sec)
    LaGG-1/3: 120 rpg (9 1/2 sec)
    La-5/7: 200 rpg (15 1/2 sec)
    Yak-1: 120 rpg (9 1/2 sec)
    P-38: 150 rpg (15 sec)

    With the exception of the Hurricane, early Zeros and early Spitfire Vb, most fighters carried more than 100 rpg for their cannon.

    Most assesments put 20mm cannon at around 2.5-4 times more powerful than any single .50 calibre weapon. This is generally because of their capacity to carry far larger amounts of HE, while maintaining a relatively high RoF. In terms of power round for round, 20mm rounds are generally assesed as 3-4 times more destructive than their 12.7mm counterparts.

    So, while most 20mm armed fighters don't carry around the quantity of ammunition that .50 armed fighters do, they tend to get more 'bang for their buck', so to speak. For example, the 120 rpg loadout on most Spitfires was the equavilent to a total of around 800-1100 rounds of .50 calibre ammunition, depending on how you measure the effectiveness. More destruction, for less weight and less time on target.

    The homogenous .50cal armament was really only used by the USA, and that was primarily a function of them not having an effective alternate. Most nations went to the 20mm as their primary fighter armament, with either RCMGs or HMGs providing back up.
     
  12. lesofprimus

    lesofprimus Active Member

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    I prefer 20mm cannon as well, although 8 x .50's for strafing is just insane.....
     
  13. syscom3

    syscom3 Pacific Historian

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    Les, imagine a B25 or A26 gunship coming at you with a dozen .50's.
     
  14. lesofprimus

    lesofprimus Active Member

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    Trust me, I have, and talked to guys who held the trigger down... Insane damage...
     
  15. Glider

    Glider Well-Known Member

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    Or the good old Beaufighter. Working on the three 0.5 = one 20 principle

    4 x 20 and 4 x 0.5 = 16 x 0.5. No wonder it was called the whispering death
     
  16. R988

    R988 Member

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    add in some rockets for good measure as well....
     
  17. Jabberwocky

    Jabberwocky Active Member

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    Only Aussie built Beaufighters had 4 x .50 and 4 x 20mm. Most of the British built ones had 6 x .303 (two in the left wing and four in the right) and 4 x 20mm. Less weight of fire and penetration, than with the .50s, but more actual rounds zinging around the place. 6 .303s would put out about 7,200 rounds per minute. In a 2 second firing run a Beaufighter would put out around 240 .303 rounds punctuated with 80 20mm rounds, for a grand total of about 13kg of lead.

    The P-61 and F7F were just as scary though, both hauled around 4 x .50 and 4 x 20mms. In a 2 second firing run they would put out about 104 .50 cal rounds and 80 20mm rounds, for a grand total of about 15kg of lead.

    Mosquito wasn't far off either with 4 x .303 and 4 x 20mm, with an absolute stack of ammo for both as well.
     
  18. Twitch

    Twitch Member

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    American pilots liked the 20 mm weapon when they had it. P-38, Spit, and F6F pilots I know were happy with it as they should be. Of course they were mixed with .50 cals. None gave a bucket of spit for .30s no matter how many were mounted.

    I still stand by the statement, "Frankly it didn't matter if a "good" grade pilot took 700 rounds to bring down an enemy with fifties where an elite pilot used 70 rounds of 20 mms." - Because you gotta be good enough to put ordnance on target in the first place, it matters not what caliber gun you got. An "average" skill shooter can simply procure more hits with fifties than with 20s because he's not hording rounds.

    Idealy 20/50s would be the perfect armament. You range in and begin damaging with the fifties and touch the cannon trigger to follow up. Repeat as necessary for results.

    It is interesting to note that even cannon-trained air forces like the Luftwaffe continued to mount .30/.50 calibered weapons in addition to cannon. They were there for 2 reasons- to range in and to actually shoot down E/A when cannon shells were gone. Of course almost immediately .30 caliber was obsolete as a killing tool in WW 2. If the half inch caliber wasn't better the Luftwaffe wouldn't have used them on Bf 109s and Fw 190s in place of the .30 cal equivenent- MG 131 vs MG 17.
     
  19. Erich

    Erich the old Sage
    Staff Member Moderator

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    side note :

    P-61's in the Pacific only had the 4 .50's installed in the upper turret fitting

    ETO P-61 squadrons flet they did not need the .50's as the 4 20mm were enough which they were plus no aerodynamic drag or weight of the upper installation

    E
     
  20. Twitch

    Twitch Member

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    More trivia- In WW II three P-61 gunners each scored five- Lt. Edward Kospel, Lt. Robert Tierney and Lt. Philip Porter.
    [​IMG]
     
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