Aircraft Machine Gun vs. Cannon?


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dk-corriveau
September 15, 2006, 10:31 PM
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:

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Tory
September 15, 2006, 10:34 PM
solid projectiles. They do not explode.

Cannons shoot shells; they DO explode!

thexrayboy
September 15, 2006, 10:38 PM
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.

pete f
September 15, 2006, 10:45 PM
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.

R.W.Dale
September 15, 2006, 10:46 PM
In short machine guns poke holes in other aircraft, where as cannons tend to do more "blowing up" of enemy aircraft.

Josh Aston
September 16, 2006, 12:20 AM
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.

Tory
September 16, 2006, 12:37 AM
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.

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

A cannon is any large tubular firearm designed to fire a heavy projectile over a considerable distance. The term can apply to a modern day rifled machine gun with a calibre of 20 mm or more (see autocannon).

- Wikipedia

The exploding ordnance is the key distinction.

44AMP
September 16, 2006, 12:51 AM
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.

Lucky
September 16, 2006, 01:38 AM
http://www.quarry.nildram.co.uk/

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.

Oleg Volk
September 16, 2006, 02:23 AM
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).

Josh Aston
September 16, 2006, 03:15 AM
Then how is it that 20MM guns are referred to as "cannon;" i.e., the Vulcan Autocannon?

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.

BruceB
September 16, 2006, 03:32 AM
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.

Deanimator
September 16, 2006, 09:18 AM
Cannon also have a greater effective range.
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.

Fosbery
September 16, 2006, 09:31 AM
Four .50 cal machienguns next to a 75mm cannon on a B-25H bomber.

http://www.aerovintage.com/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.

Apple a Day
September 16, 2006, 09:58 AM
...but why is one a machine gun and one a cannon?

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:

Tory
September 16, 2006, 10:57 AM
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).

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:

Fosbery
September 16, 2006, 11:14 AM
Medievel to 18th century muzzle loaders then.

default
September 16, 2006, 11:32 AM
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.

MudPuppy
September 16, 2006, 12:32 PM
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.

MachIVshooter
September 16, 2006, 01:13 PM
Then how is it that 20MM guns are referred to as "cannon;" i.e., the Vulcan Autocannon?

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.

Tory
September 16, 2006, 01:32 PM
Vulcan is 30mm (used in the A-10)

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

Best check this:

20 mm Weapons

Each weapon is listed with its cartridge type appended.

Current Weapons

* M61 Vulcan - 20x102
* M197 Gatling gun 20x102
* Oerlikon KAA - 20x128
* Rheinmetall MK20 Rh202 - 20x139

Quickseek

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

SDC
September 16, 2006, 01:40 PM
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).

Lennyjoe
September 16, 2006, 05:43 PM
The A-10 uses a GAU-8 30MM gun.

http://www.imagestation.com/picture/sraid62/p4a5a0e52b306219cd39f400a3dbbdb11/fc22b66c.jpg

http://www.imagestation.com/picture/sraid204/p43efd033203002d2c693339a4470f7d9/ef496ff7.jpg

Autolite
September 16, 2006, 05:59 PM
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 ...

Fosbery
September 16, 2006, 06:48 PM
^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.

Jim K
September 16, 2006, 10:48 PM
There is no rule. The terms go back to the early days when 20mm was the smallest projectile that could hold a fuze and a reasonable amount of explosive, so it was called a "cannon" as opposed to (then) rifle caliber machineguns which fired inert projectiles. Later, explosive bullets were made for both rifle caliber and larger (e.g., .50 cal, 12.5mm) machineguns, but the names and distinctions stuck.

Jim

Gifted
September 16, 2006, 11:58 PM
Most source books I"ve read say that cannon start at 20mm. I think that's a NATO thing, so other people might draw the line in a different place.

MachIVshooter
September 17, 2006, 12:37 PM
IIRC the 20mm M61A1 is called the "Vulcan" whereas the 30mm as used by the A-10 is called the "Avenger".

I stand corrected.

But do a search for "30mm Vulcan cannon", and you'll see that it was contrived from much available misinformation. A couple examples:

http://www.bigskysurplus.com/30mm.htm

http://www.windy-city.com/ajsworld/knobcreek/vulcan.htm

http://www.montysminiguns.com/RealityPage.htm

It also has been refferred to this way on more than one documentary-type shows from History channel, Discovery channel, etc.

It would seem that the "Vulcan" name has been applied to more than one of the Gatling-type cannons, if only informally.

Gifted
September 18, 2006, 06:21 AM
Yup, and there's also only one Minigun. While people use the term to refer to just about any gatling type, there's only one that's actually named that. Just like most modern ones aren't really gatling guns-unless Gatling has come back from the dead and started making them again.

Deanimator
September 18, 2006, 10:48 AM
Yup, and there's also only one Minigun.

I'm partial to the "Six Pak", the 5.56 version!

Manedwolf
September 18, 2006, 11:43 AM
A couple of WWII aircraft mounted a 75mm cannon in the nose :what: I've seen photos of an A-26 Invader with one, and I belive they tried it with a few others.

Hell of a bang...

buzz_knox
September 18, 2006, 12:29 PM
[QUOTE]It would seem that the "Vulcan" name has been applied to more than one of the Gatling-type cannons, if only informally.
/QUOTE]

The original Vulcan was the project to implement the addition of electric power to the Gatling style of rotary barrels. Although this had been done previously (around the turn of the 20th Century), the Vulcan was the first project done with the intent of making it a service weapon as opposed to an experiment. The M61 Vulcan 20mm cannon was the result. Subsequently, other rotary style electric weapons (and some gas operated weapons as used in gun pods) became known as Vulcans. The 30mm GAU-8 mounted on the A-10 was a follow on.

As for the cannon/machine gun distinction, the reason behind it was varied. It was not a matter of solid versus explosive rounds, since explosive and explosive/incendiary rounds were widely available for rifle caliber weapons (and which were regulated by the Hague Accords). As a rule of thumb, machine guns fired rifle caliber rounds, or slightly larger than rifle caliber. Cannons fired rounds significantly larger than rifle caliber.

As for the preferences of the military, it depends on what period one is discussing. In the early stages, the rifle caliber machinegun was king due to increased rate of fire and range, and aircraft size (both of the type using the weapon and the type to be shot down). As weapons and aircraft technology progressed, different militaries were concerned with different goals. The 30mm and larger cannons were principally used by militaries concerned with shooting down bombers (Germany during the war and the Soviet Union and European nations after it). The explosive rounds were more effective on destroying large sections of aircraft with single hits. The rifle caliber machineguns were used by those nations more concerned with destroying fighters, usually during escort missions for bombers (the US, which cooked the books on .50 performance to justify its use even after the 20mm was known to be superior for the role), although the Russians preferred larger calibers for anti-fighter duty, as they would tend to close the range and try to use single rounds for the kills.

DF357
September 18, 2006, 12:42 PM
Handheld gunpowder fired weapons were originall called "hand cannons'.

Notice they were also called 'gonnes'



http://en.wikipedia.org/wiki/Gonne

Gifted
September 20, 2006, 03:19 PM
Something else to think about is firing time. With the 300 rounds loaded on the Spitfire, you had thirty seconds of firing time. The lower rate and less ammo of cannon would reduce this to some extent. increasing the rate of fire increases the efficiency of each second, though at a cost. The F-16 carries 510 rounds, more than any WWII plane, but at 6000 rounds a minute, that only lasts FIVE seconds.

buzz_knox
September 20, 2006, 03:24 PM
The F-16 carries a large amount of ammunition, but this is in part due to perceived lack of effectiveness of the 20mm round against modern aircraft. Combined with the reduced practicality of the M61 (which, even in the lighter M61A2 version, takes sufficient time to work up to operating speed that the required concentration of fire might not be available against modern aircraft), you need a fair amount of ammunition.

wingnutx
September 20, 2006, 03:36 PM
The coming replacement for the M2 machine gun will fire fused projectiles that can do a mini air-burst over a target that is behind cover.

Behold the XM307 (http://www.defenseindustrydaily.com/2005/11/xm307-madeuce-replacement-gets-more-investment/index.php), which also is supposed to replace the MK19.

IIRC, there is a shoulder-fired weapon being tested that will do the same thing. You feed in the range you want the shell to burst at.

crunker
September 20, 2006, 05:09 PM
I find that the difference between cannons and high-caliber machineguns is that machineguns, even the high-caliber ones, can be transported and operated by no more than two people. They are small arms.
Cannons require a mounting vehicle to absorb the heavy recoil, and to my knowledge, 20mm is never used as a small arm.

deadly50bmg
September 20, 2006, 08:38 PM
keep looking. lahti makes a 20mm AMW that is shoulder fired

Detritus
September 21, 2006, 12:59 AM
the US, which cooked the books on .50 performance to justify its use even after the 20mm was known to be superior for the role

if you're talking about WW2-korea era fighter useage, that was in large part b/c the hispano-suiza HS.404 variants built in the US were unreliable (stoppages due to light primer strikes being common, amoung other issues) and the US declined to take the measures that the British had used to up reliability, ie shortened chambers and oiled ammo.

the US adopted large scale 20mm use in the mid 50's with the USAF's M-39 rotory chamber cannon and the Navy's Colt Mk12 (a HS.404 variant that continued to suffer jams and stoppages esp. during or after dogfight manuvering)

DerringerUser
September 21, 2006, 01:31 AM
http://www.globalsecurity.org/military/systems/aircraft/images/a-10_gattling-gun_040302-f-3963c-059.jpg


A-10

Priceless.

buzz_knox
September 21, 2006, 09:32 AM
[if you're talking about WW2-korea era fighter useage, that was in large part b/c the hispano-suiza HS.404 variants built in the US were unreliable (stoppages due to light primer strikes being common, amoung other issues) and the US declined to take the measures that the British had used to up reliability, ie shortened chambers and oiled ammo.

If memory serves, the issue wasn't reliability but rate of fire and effectiveness. At the time, the Army Air Corps described the 20mm cannons as having a rate of fire far lower than what in fact they were capapble of, and not due to stoppages.

superhornet
September 21, 2006, 02:36 PM
USNAVY=M61A1 & M61A2 LWC.......

Gifted
September 27, 2006, 06:39 PM
The F-16 carries a large amount of ammunition, but this is in part due to perceived lack of effectiveness of the 20mm round against modern aircraft. Combined with the reduced practicality of the M61 (which, even in the lighter M61A2 version, takes sufficient time to work up to operating speed that the required concentration of fire might not be available against modern aircraft), you need a fair amount of ammunition.Even so, the high rate of fire means that you only have five seconds to hit the target. With the WWII planes, they generally had thirty or more. Now with missiles, the gun becomes a last resort(and like I've been told, if you're alone and use up four or more missiles, something's wrong that won't be fixed with a gun), or for ground targets of oppurtunity. In which case the lower engagement times become irrelavent.

oneshooter
September 27, 2006, 08:38 PM
I don't believe that you can match the brutal firepower of a gun nosed B-26.

http://www.thehighroad.org/attachment.php?attachmentid=45477&stc=1&d=1159399808

Oneshooter
Livin in Texas

Macpherson
September 29, 2006, 05:28 AM
Holy crap! Far be it from me to question WW2 firepower, but what possible use does a high level bomber have for 8 .50 cals in the nose? Did they take it on strafing runs or what?

On another note, that must've been lots of fun for the pilots when those things were firing :what:

jack the toad
September 29, 2006, 09:17 AM
Not for sure on any of this and don't know the correlation, if any, between military and ATF regulations but isn't anything over .50 cal. considered a destructive device, ie; cannon, grenade, 20m/m and larger, etc.?
ATF lists some 12 gauge shotguns as DD.

buzz_knox
September 29, 2006, 09:41 AM
Holy crap! Far be it from me to question WW2 firepower, but what possible use does a high level bomber have for 8 .50 cals in the nose? Did they take it on strafing runs or what?

The B-26 was not used as a high level bomber, but as a low to mid level bomber/strike aircraft. The .50s were used for ground attack and train busting. The B-25 ground attack variants were similarly armed (with a few carrying a 75mm cannon) and used for anti-shipping work as well.

TimboKhan
September 29, 2006, 09:44 AM
I find myself oddly fascinated by this thread. I have always sort of wandered what made a cannon a cannon....

Keith Wheeler
September 29, 2006, 09:55 AM
Please no one ask the difference between an autocannon and an automatic grenade launcher!

:) :evil:

Ash
September 29, 2006, 10:10 AM
Yeah, B-25, B-26, and A20 Havocs all came in a ground attack mode. The B25 not only had the nose filled with 50 calibers, but had four fusilage mounted 50s that fired foreward as well. These were the forerunners of the A-10 and were very effective (except they weren't designed for anti-tank).

Many rifle caliber rounds were designed with exploding bullets (though not meant for rifles) such as the 7.62x54R (though when I fire my 91/59, folks think I'm firing a cannon):D

Ash

Ash
September 29, 2006, 10:13 AM
Those bombers were tactical bombers meant to be employed on the battlefield and were very successful. Stratiegic bombers such as the 17, 24 and 29 were miserable in tactical combat roles (the B29 was pathetic in Korea when applied to tactical jobs). The B17's were of no real value at Midway and didn't do much at Normandy either. But, the medium bombers were very effective in ground and sea attack.

Ash

buzz_knox
September 29, 2006, 10:56 AM
Please no one ask the difference between an autocannon and an automatic grenade launcher!

The velocity and nature of the round are the key differences.

Yeah, you didn't ask, but you did mention. Same thing. :evil:

oneshooter
September 29, 2006, 08:31 PM
My Dads unit in Korea, 13th Bombardment Squadron (Light) used both B-25's and later B-26's. The Mitchell carried 8 fifties in the nose, 2 mounted on each side of the fusalage, and the top turret could be locked forward and controlled by the same trigger. Thats 14 50 cals, 600rpm EACH, and 1200rds available for EACH weapon!! Thats the same firepower as a Battalion of troops. Plus 4 500lb bombs!! They flew low level interdiction missions, both day and night.
http://www.thehighroad.org/attachment.php?attachmentid=45582&stc=1&d=1159572049

Notice the 80 million candlepower NAVY searchlight under the wing, you can't hit what you can't see!
The Northmen hated and feared these planes.
Oneshooter
Livin in Texas

AaronE
September 30, 2006, 12:40 AM
was used to GREAT efficacy in the Pacific. the ones with the 75mm made GREAT barge busters and anti-shipping aircraft.

:eek:

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