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Aircraft Machine Gun vs. Cannon?

Discussion in 'General Gun Discussions' started by dk-corriveau, Sep 15, 2006.

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  1. dk-corriveau

    dk-corriveau Member

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    I am watching a show tonight about Dogfights, this portion of the story is about WWII, and the voice over refers to 50 cal. machine guns (obviously a Browning) and 30mm cannons. So it got me thinking, in this context, what is the difference between the two?

    Obviously there is a difference in ammunition diameter, but why is one a machine gun and one a cannon? I can only assume that the difference is in the details of the repeating action that makes the distinction between a machine gun and cannon. Any thoughts or insights? :confused:
     
  2. Tory

    Tory member

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    The machine gun shoots bullets; i.e.,

    solid projectiles. They do not explode.

    Cannons shoot shells; they DO explode!
     
  3. thexrayboy

    thexrayboy Member

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    Cannon also have a greater effective range. Germans fighters armed with cannon could knock US bombers out of the sky without having to enter the effective range of the 50bmg guns the bombers used for defense.
     
  4. pete f

    pete f Member

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    Xray., that may be true of the guns used then but the true difference is that one shoots exploding munitions, the other just lead and jacket bullets.

    Cannon as described referring to aircraft mean that they shoot or can shoot projectiles that contain an explosive mix.
     
  5. R.W.Dale

    R.W.Dale Member

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    In short machine guns poke holes in other aircraft, where as cannons tend to do more "blowing up" of enemy aircraft.
     
  6. Josh Aston

    Josh Aston Member

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    I believe that to be considered a cannon a firearm must have a bore diameter greater than 1 inch (25mm). 20mm guns generally have explosive shells and there may even be some explosive shells out there for the .50, but since neither is over an inch in diameter they wouldn't be cannons.
     
  7. Tory

    Tory member

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    Really?

    Then how is it that 20MM guns are referred to as "cannon;" i.e., the Vulcan Autocannon? :scrutiny:

    - Wikipedia

    The exploding ordnance is the key distinction.
     
  8. 44AMP

    44AMP Member

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    Cannon

    The difference, in small arms, is cannon can fire explosive shells, rifles and machineguns cannot. In artillery it is different. Since artillery normally fires explosive shells, technically they are all cannon. So artillery pieces are named after their prinicple purpose. And the term cannon is sometimes used, but sometimes they are just called "gun" Tank cannon are usually called "guns". There are (or used to be) anti-aircraft guns. Howitzers are a certain class of "gun" Naval cannons are called "guns", or "rifles".

    Mortars and grenade launchers seem to be in their own category, as they are never called guns or cannon.

    20mm is the smallest cannon used by our military during the last century or so. Other countries weapons are usually described in our terms.

    Aircraft guns during WWII run from rifle caliber (.30, .303, 7.7mm, 8mm, etc) up to heavy machinegun (.50cal, 13mm, etc) and then to 20mm cannon. 30mm, 37mm, 50mm, and even 75mm guns were mounted in or on aircraft by different countries during the war.

    Most German fighters mounted 20mm and later 30mm cannon. There were also tank buster Stukas that carried a pair of 37mm cannon, and a few late war "bomber-destroyers" that carried a cannon as large as 50mm.

    US fighters mostly used machineguns, but there were a couple that carried a cannon as well. The P-38 carried a 20mm cannon, along with .50 cal machineguns. The P-39 had either a 20mm or a 37mm cannon:eek: , along with .30 and .50 cal machineguns. But most of our fighters carried either 4, 6, or 8 .50cal Browning machineguns.
    One version of the B-25 bomber carried as many as 12 .50 cals in the nose, AND a 75mm howitzer!

    While there were some cannon which outranged our .50BMG, there were many that did not. They fired at a lower velocity than the .50BMG, and so, while the shells were more destructive, they had more drop, and so, less useable range.
     
  9. Lucky

    Lucky Member

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    There don't seem to be any described rules, just when it's over 14.5mm it's common to call them cannons, but there are 'machine guns' of larger calibre, to be sure.
     
  10. Oleg Volk

    Oleg Volk Moderator Emeritus

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    Apparently, 30mm aircraft cannon had such low muzzle velocity that their combat effectiveness was low. MIGs in Korea had a hard time against Super Sabres due to that, and also due to better climate control on the F86 (i.e. no fogged up cockpits after a fast altitude change).
     
  11. Josh Aston

    Josh Aston Member

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    Hey I could be wrong, I'm no expert. The inch thing was just the first definition I ever heard for cannons, it was in some encyclopedia I read as a kid.
     
  12. BruceB

    BruceB Member

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    There are many, many designs of BULLETS (i.e.: rifle-caliber and up to .50 or so) which were used in aircraft applications.

    As early as World War One, there were some exotic designs. WW II saw armor-pierciing, armor-piercing incendiary, armor-piercing incendiary tracers, and many others, which were NOT just "lead/copper/steel" projectiles. The British even had such projectiles for their .303 Brownings, typically mounted in batteries of eight guns per fighter (Hurricane and early Spitfire).

    There were furious arguments in the RAF among the officers, air staffs and pilots concerning the relative effectiveness of eight MGs versus two or four 20mm cannon, and such notables as Douglas Bader staunchly spoke for MGs over cannon. Eventually they were over-ruled, and cannon were adopted on later Spitfires. Hurricanes were adapted to the ground-attack role, and cannon served well in that 'workplace'. The cannon's shorter range, slower cyclic rate, and reduced number of rounds carried, were offset (at least to some degree) by the heavier blow struck by each shell hitting the enemy aircraft target.
     
  13. Deanimator

    Deanimator Member

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    Actually, during WWII that wasn't the case. The 20mm cannon in the Zero had a shorter max effective range than the .50s in American aircraft. That's why the Japanese Navy pilots were so diligent about using their 7.7mm Vickers machineguns to get the range to the target before using the cannon.
     
  14. Fosbery

    Fosbery Member

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    Four .50 cal machienguns next to a 75mm cannon on a B-25H bomber.

    34106.jpg

    Personally, I prefer to think of cannons as anything that's 20mm or over. Maybe that's not the dictionary definition but I think it makes more sense. Muzzle loading cannons fired solid shot, or case shot, not explosives (I'm sure there's some obscure example of explosives bieng used but that would be incredibly rare). Modern cannons can fire sabbot rounds and other non-explosive ammunition and I'm sure there are machineguns which can fire explosive ammunition.

    It seems odd that the category a gun falls in to is defined not by the gun itself, but by the ammunition made for it. So, if just one round of explosive .22 LR was made somewhere in the world, everyone's Browning buckmarks would be cannons? I think not.
     
  15. Apple a Day

    Apple a Day Member

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    It probably has more to do with which ones were being lugged around by infantry at the time they were first described and which ones were mounted on vehicles. Anyting lugged around by a trio of groundpounders with dirty boots was a machine gun ; anything that took wheels or wings to get around counted as artillery.


    Oleg,
    They carried a 23mm cannon as well which I wouldn't sneeze at. The MiG-15 also had stability problems at high speed & altitude along with the climate control issues. My old Nissan has the same thing dadgummit (climate control issues... not a 23mm cannon I'm sorry to say 'cause that'd be AWESOME!) :what:
     
  16. Tory

    Tory member

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    MISINFORMATION

    NONSENSE. :scrutiny:

    Both spherical case and shell were in wide use by the time of the Crimean and US Civil war; the latter before then. As muzzleloaders were the primary artillery peices of the time (the Whitworth just coming into service), this ordnance is hardly "incredibly rare." :rolleyes:
     
  17. Fosbery

    Fosbery Member

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    Medievel to 18th century muzzle loaders then.
     
  18. default

    default Member

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    There's no exactingly strict definition that I'm aware of, but if one were to reserve the term for automatic weapons with a caliber greater than around .60 or roughly 15mm, often but not always known for their high muzzle velocity and use of explosive ammunition, one couldn't go too far wrong. In other words, I can think of "cannons" with low muzzle velocity (MK-108), "cannons" that fire primarily non-explosive ammunition (GAU-8), but no "cannons" with a caliber smaller than 15mm.

    We need Tony Williams to post in this thread, as he quite literally wrote the book on the subject.
     
  19. MudPuppy

    MudPuppy Member

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    As specific to aircraft of the WW2 era, the machine gun was generally a faster firing weapon with a higher velocity. It also had the ability to carry a greater ammo load. This seemed to make for a more effective anti-fighter plane weapon.

    The cannon of the era were generally lower velocity, but packed a wallop--making them pretty much a requirement for those tough heavy bombers (especially those of american and british mfg--like the B-17). The non-evasive bombers would be an easier target to hit than an agile fighter--well, except for the massed machine guns of multiple bombers spoiling your aim.

    When the war started, the transition from light 30 cal machine guns was underway (The US was ahead of the curve with most fighters equiped with 50 cal machine guns).

    There was also a wide variety of cannon types, from the common allied and german 20mm variants, to the heavy 30mm used extensively by the germans--but also included the very heavy 37mm of the P-39s and P-63s (I think it was a '63? The airacobra and king cobras...) and those were excellent against ground targets and merchant ships, all the way up to those 75mm howitzers on some models B-25s.

    Like everything, you had to give up something to get something and using the right tool for the job would make a difference.
     
  20. MachIVshooter

    MachIVshooter Member

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    Vulcan is 30mm (used in the A-10)

    Phalynx system cannon is 20mm; when not used in this system it is often referred to as the 20mm gatling gun.
     
  21. Tory

    Tory member

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    Really?

    Best check this:

    And it's "Phalanx" and "Gatling." ;)
     
  22. SDC

    SDC Member

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    Historically, the "cannon" designation seems to only come into use after the projectile size is 15mm or more (which is also the point at which a useful (damage-wise) amount of explosive can be packed into that projectile. There are counter-examples on both sides of this equation though; the 15mm BESA machinegun (as far as I'm aware) never used any explosive-filled shells, while projectiles smaller than 15mm have also been packed with explosives, such as the .30-calibre 7.65 Arg Mauser and 8mm Mauser rounds, and the 13mm MG131s on later versions of the FW190 (which used standard-pattern fused ammunition).
     
  23. Lennyjoe

    Lennyjoe Member

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    The A-10 uses a GAU-8 30MM gun.

    [​IMG]

    [​IMG]
     
  24. Autolite

    Autolite Member

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    IIRC the 20mm M61A1 is called the "Vulcan" whereas the 30mm as used by the A-10 is called the "Avenger". Anyway, the book "Flying Guns Of WWII" pretty much answers all the questions. In a nutshell, (not counting exploding rounds), I believe an aircraft's ability to destroy an adversary was determined by the mass and energy the gun system could deliver at a given range within a specific time span. Whether machine gun, cannon or both, the determining factor was how much lead could be poured out and at how hard did the projectile hit ...
     
  25. Fosbery

    Fosbery Member

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    ^Autolite has the right of it as regards the Vulcan and Avenger.

    THe RAF started the war with .303 machineguns. It considered moving to .50 cal but felt it was a waste as it did not provide any real improvement over the existing .303s. The RAF instead moved to 20mm Hispano-Suiza cannons in combinateion with the .303s before removing the .303s completely and replacing them with more 20mms.
     
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