Machine Gun vs Cannon: Definition

[Chris]

Can somebody provide a simple explanation of the difference between a
machine gun (ex .50 or .303 on Allied aircraft) and cannon (ex 20mm on
German a/c).

I used to think cannons shot explosive rounds and guns shot kinetic
energy rounds, but I saw a show on TV comparing .303 to 20mm and the
20mm seemed to be shooting kinetic energy rounds. Also the A10
Warthog has a "cannon" that shoots inert heavy metal rounds. Now I'm
confused.

Is the size of the round the determining factor? Greater than
12mm/.50 cal is a cannon?

Thanks,
Chris
--

[Eystein Roll Aarseth]

Post by Chris
Can somebody provide a simple explanation of the difference between a
machine gun (ex .50 or .303 on Allied aircraft) and cannon (ex 20mm on
German a/c).
I used to think cannons shot explosive rounds and guns shot kinetic
energy rounds, but I saw a show on TV comparing .303 to 20mm and the
20mm seemed to be shooting kinetic energy rounds.

Well, strictly speaking all projectile weapons use kinetic energy to
damage their targets; it's just that some of them use explosives or
incendiaries inside the projectile to increase the damage done. :-)

Post by Chris
Also the A10 Warthog has a "cannon" that shoots inert heavy metal
rounds. Now I'm confused.

And then there's Nammo's (www.nammo.no) 12.7mm MultiPurpose
ammunition to further confuse the issue... oh, and a Napoleonic-era
long-barreled 32-pounder is still a "cannon" even though it (usually)
fired solid iron balls... (if it is a short-barreled 32lber it may
be called a "carronade", but that's a discussion for another NG...)

Post by Chris
Is the size of the round the determining factor? Greater than
12mm/.50 cal is a cannon?

More or less. I'd say that anything below 20mm is a machine gun,
20mm and up is a cannon. (I've never seen the Russian 14.5mm described
as anything other than a heavy machine *gun*, at least...)

It's just one of those weird rules that someone made deep in the mists
of time; Nobody really knows who, when and why, we just go along with
it because "that's the way it's always been"...

EAa

[Michele Armellini]

Post by Chris
Can somebody provide a simple explanation of the difference between a
machine gun (ex .50 or .303 on Allied aircraft) and cannon (ex 20mm on
German a/c).
I used to think cannons shot explosive rounds and guns shot kinetic
energy rounds, but I saw a show on TV comparing .303 to 20mm and the
20mm seemed to be shooting kinetic energy rounds. Also the A10
Warthog has a "cannon" that shoots inert heavy metal rounds. Now I'm
confused.

It's not the round type. a .50 cal MG can fire explosive ammo and a 75mm
tank gun can fire a kinetic-energy AP round.

Post by Chris
Is the size of the round the determining factor? Greater than
12mm/.50 cal is a cannon?

Yes, roughly. There are MGs around 13-14mms in caliber, and they are called
MGs. However, the 20mm or 30mm weapons you mentioned are more correctly
defined as _auto_-cannons. A "cannon" might well be a larger-bore gun that
requires a crewman to manually reload it. Autocannons rely on some form of
automatic fire, like machine guns.
--

[ian maclure]

Post by Chris
Can somebody provide a simple explanation of the difference between a
machine gun (ex .50 or .303 on Allied aircraft) and cannon (ex 20mm on
German a/c).
I used to think cannons shot explosive rounds and guns shot kinetic
energy rounds, but I saw a show on TV comparing .303 to 20mm and the
20mm seemed to be shooting kinetic energy rounds. Also the A10
Warthog has a "cannon" that shoots inert heavy metal rounds. Now I'm
confused.

There are other natures though and the Warthog gun is an
airborne AT gun.

Post by Chris
Is the size of the round the determining factor? Greater than
12mm/.50 cal is a cannon?

The definition is kind of loose.
I basically say its a cannon if the primary ammunition
nature against all targets is a solid ball projectile.
In short does the gun have a commonly used HE shell.
Tracer/Incendiary does not count against this definition.
So a .50/12.7 which is basically a solid ball gun is
an MG.
A 15mm is probably an MG but...
A 20mm is probably a cannon but.
Above that the distinction is clearer I think.

IBM

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[Cub Driver]

Post by Chris
Can somebody provide a simple explanation of the difference between a
machine gun (ex .50 or .303 on Allied aircraft) and cannon (ex 20mm on
German a/c).

There is no absolute distinction. Generally speaking, anything larger
than half-inch or 12.7 mm is considered a cannon, and a cannon of
course almost always had an explosive shell. (There were explosive
shells for machine guns as well.)

The smallest WWII-era cannon I have seen mention of was 18 mm. That
would have been about 0.71 caliber. I think I have read about a 13 mm
machinegun, which would have been 0.51 caliber.

all the best -- Dan Ford
email: ***@mailblocks.com (put Cubdriver in subject line)

Warbird's Forum www.warbirdforum.com
Piper Cub Forum www.pipercubforum.com
the blog www.danford.net
--

[Dave Gower]

Post by Cub Driver
The smallest WWII-era cannon I have seen mention of was 18 mm.

Actually, the Germans fitted a 15mm MG151 into the nose of the Me109 F-1,
introduced in 1941. It actually replaced the 20mm nose cannon of earlier
variants. This was done both to reduce vibration and because the 15mm weapon
had a higher velocity and flatter trajectory than the 20mm. In the hands of
a really skilled marksman it was a good selection, but many pilots preferred
the hitting power of the larger weapon which became standard by the F-4
variant.

--

[Nicholas Smid]

Post by Dave Gower

Post by Cub Driver
The smallest WWII-era cannon I have seen mention of was 18 mm.

Actually, the Germans fitted a 15mm MG151 into the nose of the Me109 F-1,
introduced in 1941. It actually replaced the 20mm nose cannon of earlier
variants. This was done both to reduce vibration and because the 15mm weapon
had a higher velocity and flatter trajectory than the 20mm. In the hands of
a really skilled marksman it was a good selection, but many pilots preferred
the hitting power of the larger weapon which became standard by the F-4
variant.

The 15mm MG151 is probably the smallest meant to be a cannon, the normal
change over is 20 mm, though argument is ongoing. But the main point about
the MG151 was it was a new generation of gun replacing the pre war Olikons
in German service, it had much higher MV and was all round a better gun. The
Bf 109F-4 still carrier an MG151 but it had been bored out to take a new 20
mm round, the 15 mm necked up I think, less MV but more punch, went into the
FW190 too.

[Cub Driver]

On Sat, 20 Nov 2004 00:43:45 +0000 (UTC), "Dave Gower"

Post by Dave Gower
Actually, the Germans fitted a 15mm MG151 into the nose of the Me109 F-1,
introduced in 1941.

But was it considered a cannon or a machine gun?

Thanks for the information. I can now narrow the gap between the two
weapons even further, if only 13 mm and 14 mm are in the gray area.

all the best -- Dan Ford
email: ***@mailblocks.com (put Cubdriver in subject line)

Warbird's Forum www.warbirdforum.com
Piper Cub Forum www.pipercubforum.com
the blog www.danford.net
--

[Cub Driver]

According to Robert Mikesh in Japanese Aircraft Equipment, 1940-1945,
the Japanese regarded anything larger than 11 mm to be a machine
cannon.

all the best -- Dan Ford
email: ***@mailblocks.com (put Cubdriver in subject line)

Warbird's Forum www.warbirdforum.com
Piper Cub Forum www.pipercubforum.com
the blog www.danford.net
--

[tim gueguen]

Post by Cub Driver
. I think I have read about a 13 mm
machinegun, which would have been 0.51 caliber.

That would be the German MG131, which was used in both fixed and flexible
mountings in aircraft in the latter stages of the war, such as in later
version of the Focke-Wulf FW190. The Russians had a 14.5mm antitank rifle
cartridge that was used after WW2 as a machine gun cartridge in the KPV
heavy machine gun.

tim gueguen 101867
--

[dp]

Post by tim gueguen

Post by Cub Driver
. I think I have read about a 13 mm
machinegun, which would have been 0.51 caliber.

That would be the German MG131, which was used in both fixed and
flexible mountings in aircraft in the latter stages of the war, such
as in later version of the Focke-Wulf FW190. The Russians had a
14.5mm antitank rifle cartridge that was used after WW2 as a machine
gun cartridge in the KPV heavy machine gun.
tim gueguen 101867
--

I've also seen the 13mm Mg131 referred to as a "Machine Cannon"

[Taki Kogoma]

On Sat, 20 Nov 2004 00:44:02 +0000 (UTC), tim gueguen <***@shaw.ca>
allegedly declared to soc.history.war.world-war-ii...

Post by tim gueguen
That would be the German MG131, which was used in both fixed and flexible
mountings in aircraft in the latter stages of the war, such as in later
version of the Focke-Wulf FW190. The Russians had a 14.5mm antitank rifle
cartridge that was used after WW2 as a machine gun cartridge in the KPV
heavy machine gun.

And then there's the 15mm Besa MG mounted on some british armoured
cars and light tanks.

[Martin Rapier]

"Taki Kogoma" <***@swcp.com> wrote in message news:cnrmoj$nju$***@gnus01.u.washington.edu...
{snippity}

Post by Taki Kogoma
And then there's the 15mm Besa MG mounted on some british armoured
cars and light tanks.

And which was definitely a Heavy MG rather than an autocannon.

Personally I'd put the cutoff at 20mm, even if the German did classify their
20mm autocannons as MGs!

Cheers
Martin

[Peter Larsen]

The Germans had two versions of the MG 151: the MG 151/20, and the MG
151/15. Both were cannons, of 20mm and 15mm respectively.

Indeed, the Russians used (use?) a 14,5 mm machine gun.

So I guess you can put the limit at 15 mm, so far, anyway.

Post by Cub Driver

Post by Chris
Can somebody provide a simple explanation of the difference between a
machine gun (ex .50 or .303 on Allied aircraft) and cannon (ex 20mm on
German a/c).

There is no absolute distinction. Generally speaking, anything larger
than half-inch or 12.7 mm is considered a cannon, and a cannon of
course almost always had an explosive shell. (There were explosive
shells for machine guns as well.)
The smallest WWII-era cannon I have seen mention of was 18 mm. That
would have been about 0.71 caliber. I think I have read about a 13 mm
machinegun, which would have been 0.51 caliber.
all the best -- Dan Ford
Warbird's Forum www.warbirdforum.com
Piper Cub Forum www.pipercubforum.com
the blog www.danford.net
--

[Cub Driver]

Robert Mikesh has created another of those remarkable books from
Schiffer, and unlike most Schiffer books it is farily free from
typographical and grammatical errors.

Japanese Aircraft Equipment, 1940-1945

In the chapter on machine guns, he notes that the Japanese called
anything over 11 mm a machine cannon. So the standard heavy machine
gun of 12.7 or 13 mm were, by their reckoning, cannon.

Indeed, the Navy Type 3 was 13.2mm. There was even a Navy experimental
gun (14-shi) with a 20 mm Oerlikon necked down to 14 mm. I suppose
that would rate as a cannon by both the Japanese and the western
definitions.

Mikesh's book, by the way, resolves a debate about the large-caliber
gun in the early Ki-43 Hayabusa or Oscar fighter. Japanese pilot
accounts relate that it was so slow-firing that in some planes the
weapons were field-refitted to 7.9 mm. Yet western experts say the gun
was suitably quick-firing.

Mikesh notes that the Army Type 89 7.7mm fixed machine gun was a
Vickers type that "synchronized well." The Army Type 1 12.7mm (also
called 13 mm and Ho-103) wedded an Italian 12.7 mm cartridge to a U.S.
Model 1921 Browning mg ("no mean feat", says Mikesh). "Like all
Brownings, the gun did not synchronize well, losing much of its rate
of fire."

Whereas the 7.7mm fired 900 rounds per minute, the 12.7mm when
synchronized to fire through the propeller had a rate of fire as low
as 400 rpm even though its theoretical rpm in wing mount was also 900.
This would explain the vastly different accounts given by experts in
an office and pilots in the field, and why a pilot might prefer the
smaller caliber gun.

all the best -- Dan Ford
email: ***@mailblocks.com (put Cubdriver in subject line)

Warbird's Forum www.warbirdforum.com
Piper Cub Forum www.pipercubforum.com
the blog www.danford.net

[G. Prater]

Don't forget the infamous 1.1" U.S. machine gun of early WWII used
extensively as an AA weapon.

Post by Cub Driver

Post by Chris
Can somebody provide a simple explanation of the difference between a
machine gun (ex .50 or .303 on Allied aircraft) and cannon (ex 20mm on
German a/c).

There is no absolute distinction. Generally speaking, anything larger
than half-inch or 12.7 mm is considered a cannon, and a cannon of
course almost always had an explosive shell. (There were explosive
shells for machine guns as well.)
The smallest WWII-era cannon I have seen mention of was 18 mm. That
would have been about 0.71 caliber. I think I have read about a 13 mm
machinegun, which would have been 0.51 caliber.
all the best -- Dan Ford
Warbird's Forum www.warbirdforum.com
Piper Cub Forum www.pipercubforum.com
the blog www.danford.net
--

[Scott M. Kozel]

Post by G. Prater
Don't forget the infamous 1.1" U.S. machine gun of early WWII used
extensively as an AA weapon.

It's design dated back to 1929.

1.1"/75 Calibre Machine Cannon
http://www.de220.com/Armament/1.1%20Inch/1-1Inch.htm

[Don Phillipson]

Post by Chris
Can somebody provide a simple explanation of the difference between a
machine gun (ex .50 or .303 on Allied aircraft) and cannon (ex 20mm on
German a/c).
I used to think cannons shot explosive rounds and guns shot kinetic
energy rounds, but I saw a show on TV comparing .303 to 20mm and the
20mm seemed to be shooting kinetic energy rounds.

Explosive rounds define the difference, not calibre
(barrel diameter.)
MG ammunition also includes tracer and other
"pyrotechnic" ammunition designed to be visible
or to promote burning, etc.: but weapons specialists
treat these as solid shot for practical purposes.
You could cast 20 mm solid shot, but an explosive
round does more damage than solid shot, so no
need for 20 mm. solid shot is apparent.

The original point (say in 1939) was that rifle-calibre
solid-shot ammunition was abundantly available for
MGs. For heavier duty the RAF considered adopting
0.5 cal. solid shot MGs (as used by the USA) but
like the Germans opted instead for cannon firing
explosive shells where possible (on most aircraft
other than 4-engined bombers.)

Don Phillipson
Carlsbad Springs
(Ottawa, Canada)

[Cub Driver]

Post by Don Phillipson
MG ammunition also includes tracer and other
"pyrotechnic" ammunition designed to be visible
or to promote burning, etc.: but weapons specialists
treat these as solid shot for practical purposes.

But there were explosive shells for cal-.50 machine guns, at least in
USAAF service! Are they to be redefined as cannon, or as cannon only
when firing explosive rounds?

all the best -- Dan Ford
email: ***@mailblocks.com (put Cubdriver in subject line)

Warbird's Forum www.warbirdforum.com
Piper Cub Forum www.pipercubforum.com
the blog www.danford.net
--

[Michele Armellini]

Post by Don Phillipson
Explosive rounds define the difference, not calibre
(barrel diameter.)

I disagree.

Post by Don Phillipson
MG ammunition also includes tracer and other
"pyrotechnic" ammunition designed to be visible
or to promote burning, etc.: but weapons specialists
treat these as solid shot for practical purposes.

Special MG-caliber ammo can be fully explosive. Anyway, what would be the
"practical" purposes?

Post by Don Phillipson
You could cast 20 mm solid shot, but an explosive
round does more damage than solid shot, so no
need for 20 mm. solid shot is apparent.

You could and you would, and the explosive round does more - or less -
damage depending on the intended target. The German 28mm sPzB41 fired an
APCR round, through a squeeze-bore design. The US 37mm M-3 tank gun was
normally not issued antipersonnel (HE) rounds. If guns of this caliber had
fired HE or SAPHE rounds at their intended targets (tanks), the damage done
would have been less, not more. You want to call the 28mm a machine gun
because it only fired solid rounds?

--

[Michael Emrys]

The US 37mm M-3 tank gun was normally not issued antipersonnel (HE) rounds.

But‹to further complicate the issue‹made extensive use of a cannister
antipersonnel round. I am uncertain if the Western Allies had a cannister
round in larger calibers, but I do know that the Soviets possessed one in
76mm and possibly in other calibers as well.

Michael

[dp]

Post by Don Phillipson
Explosive rounds define the difference, not calibre
(barrel diameter.)

In common usage, but not always.
Sometimes it is the design, not the projectile that defines a cannon.

Post by Don Phillipson
...
The original point (say in 1939) was that rifle-calibre
solid-shot ammunition was abundantly available for
MGs. For heavier duty the RAF considered adopting
0.5 cal. solid shot MGs (as used by the USA) but
like the Germans opted instead for cannon firing
explosive shells where possible (on most aircraft
other than 4-engined bombers.)

There was some discussion in the US about equipping the US fighters with
either 20mm cannon or .50 caliber machine gunns. The configuration of 4-6
.50 caliber MGs put a lot of rounds in the air - each of which was cabable
of traveling through most aircraft of the day and still retaining enough
force to crack an engine block. One hit from a 20mm cannon could cause
serious damage to sheet metal, and the explosive force and shrapnel meant
you had a larger area where vital parts could be damaged by each round.
However, rate of fire was slower, and ammunition carried was limited -
typically in WWII fighters to 60-120 rpg.
The US adopted the .50 caliber MG configuration under the theory that it was
easier to hit an enemy fighter with a lot of rounds in the air each capable
of inflicting some damage that with fewer rounds each capable of inflicting
a lot of damage.

Early mark Hurricanes employing tubular construction were more resistant to
cannon damage to the frame than early mark spitfires with monocoque sheet
metal construction.

Post by Don Phillipson
Don Phillipson
Carlsbad Springs
(Ottawa, Canada)

[CH B2]

Post by dp
The US adopted the .50 caliber MG configuration under the theory that it was
easier to hit an enemy fighter with a lot of rounds in the air each capable
of inflicting some damage that with fewer rounds each capable of inflicting
a lot of damage.

The Germans, who were fighting "vier-motoren" bombers for much of the war,
found low muzzle velocity, hard-hitting cannons to be just the thing. Looking
at the examples on display at the USAF museum, I was struck at the short
barrels of the German cannons, especially the 30mm.

The Americans mostly fought fighters and smaller bombers, that were harder to
fit but easier to damage with .50 cal.
--

[Michael Emrys]

Post by Don Phillipson
Explosive rounds define the difference, not calibre
(barrel diameter.)
MG ammunition also includes tracer and other
"pyrotechnic" ammunition designed to be visible
or to promote burning, etc.: but weapons specialists
treat these as solid shot for practical purposes.
You could cast 20 mm solid shot, but an explosive
round does more damage than solid shot, so no
need for 20 mm. solid shot is apparent.

Didn't the Germans have a solid AP round for the 20mm cannon on the Pz. II,
as well as their armored cars? And of course the French among others had a
25mm AT gun firing solid shot. Then there are all those larger cannon, or
guns if you prefer, that fired solid AP rounds of various calibers.

Post by Don Phillipson
The original point (say in 1939) was that rifle-calibre
solid-shot ammunition was abundantly available for
MGs. For heavier duty the RAF considered adopting
0.5 cal. solid shot MGs (as used by the USA) but
like the Germans opted instead for cannon firing
explosive shells where possible (on most aircraft
other than 4-engined bombers.)

The RAF did in fact replace the .303 with the .50 on many of its aircraft
later in the war. The Spitfire, for example, having two 20mm and two .50
instead of the eight .303 it began with or the two 20mm and four .303 during
the middle period.

Michael

[Michael Emrys]

Post by Chris
Is the size of the round the determining factor? Greater than
12mm/.50 cal is a cannon?

If there is an official defining point, I seem to have missed it. But the
general consensus, so far as I can discern one, is that the dividing line is
somewhere around 15mm. But beware of exceptions.

Michael

[Bill Shatzer]

Chris (***@my-deja.com) writes:

-snip-

Post by Chris
Is the size of the round the determining factor? Greater than
12mm/.50 cal is a cannon?

Pretty much, although note that the Luftwaffe designated its 20mm
cannon as "MG" - Machinengewehr or machinegun - while only weapons
of 30mm received the designation MK - Machinenkanone or machinecannon.



Cheers,

--


"Cave ab homine unius libri"

[R ESTEY]

Post by Chris
Can somebody provide a simple explanation of the difference between a
machine gun (ex .50 or .303 on Allied aircraft) and cannon (ex 20mm on
German a/c).
Is the size of the round the determining factor? Greater than
12mm/.50 cal is a cannon?

The cutoff between what is considered a MG and an auto cannon is usually set
at 15mm - below 15mm (12.7/13.2/14.5mm) rounds are considered as heavy MG

15mm and above are consider as cannon. Rounds smaller than 15mm are too
small for explosive type shells with point detonating fuse. Some high
explosive rounds where developed for lighter calibers, these were usually
of the high explosive incendiary (HEI) with an incendiary filler to detonate
the small high explosive charge. This is how the 12.7 Nato Raufoss works - an
incendiary charge containing powdered zirconium is crushed on impact which
ignites. The high heat generated by the rapid burning sets off the PETN
explosive filler.

The Germans developed at 15mm version of the 20mm FF cannon for the
Messerschmitt 109 series fighters. THe F series 109 used a 15mm cannon mounted
between the cylinders of the engine and firing throught the propellor hub.

[Geoffrey Sinclair]

Chris wrote in message ...

Post by Chris
Can somebody provide a simple explanation of the difference between a
machine gun (ex .50 or .303 on Allied aircraft) and cannon (ex 20mm on
German a/c).

The short answer for aircraft armament is cannon expect to normally
fire shells filled with explosives, and machine guns fire solid shot.
Both are automatic weapons.

Of course you can design solid shot ammunition for cannons and
explosive shells for machine guns. So there is an overlap.

Post by Chris
I used to think cannons shot explosive rounds and guns shot kinetic
energy rounds, but I saw a show on TV comparing .303 to 20mm and the
20mm seemed to be shooting kinetic energy rounds. Also the A10
Warthog has a "cannon" that shoots inert heavy metal rounds. Now I'm
confused.
Is the size of the round the determining factor? Greater than
12mm/.50 cal is a cannon?

Generally speaking it looks like designing an explosive round is
uneconomic for a weapon of less than around 0.5 inches/12.7 mm.

The smallest aircraft cannon in WWII was the 15mm one fitted to
the early Bf109F. The largest machine gun appears to be the
13.2mm weapons fitted to Japanese aircraft.

The 37mm, 40mm and 50mm, even 75mm cannon fitted to WWII
aircraft were normally meant as tank busters, firing AP shells,
which still normally had a small explosive charge.

Geoffrey Sinclair
Remove the nb for email.

--

[R ESTEY]

Post by Geoffrey Sinclair
The short answer for aircraft armament is cannon expect to normally
fire shells filled with explosives, and machine guns fire solid shot.
Both are automatic weapons.
Of course you can design solid shot ammunition for cannons and
explosive shells for machine guns. So there is an overlap.

Post by Chris
Is the size of the round the determining factor? Greater than
12mm/.50 cal is a cannon?

Generally speaking it looks like designing an explosive round is
uneconomic for a weapon of less than around 0.5 inches/12.7 mm.

Problem in designing an HE (high explosive) for rounds of less than 15mm
is the small capacity of the shell and difficulty of detonating the explosive
filler. A .50 Browning weighted in at 40 grams for incendiary to 46 grams
for armour piercing. The chemical filler weighted in at 34 grains (2 gram)
for M1 incendiary (90 grains - 6 grams for M23) and only 15 grains (1 gram)
for M8 armour piercing incediary. The 15mm cannon round for M151 weights
57 grams (25 -40% more than .50). A 20mm round weights in at 90-130 grams
(the lighter shell the thin walled "Mine" shell) over 2 1/2 times .50. The
20mm mine round for F/F cannon weighted 92 grams with 20 grams explosive
filler.
--

[Moe Meantam]

Post by Chris
Can somebody provide a simple explanation of the difference between a
machine gun (ex .50 or .303 on Allied aircraft) and cannon (ex 20mm on
German a/c).

I'll throw one more source into the mix here, as it might clarify the
discussion about explosive charges in the ammunition. Or, it might
not. At any rate, it's a good site for discussion about weapon types.

Post by Chris
From http://www.paladinarmory.com/MachineGuns.htm

"Automatic Cannon - Automatic weapons firing projectiles larger than
.50 inches in diameter, including the Oerlikon 20 mm cannon and Bofors
40 mm cannon. These are generally classified by BATF as destructive
devices rather than machine guns, because their ammunition normally
contains an explosive charge."

--
Al Brennan

"If we do not change direction, we will end up where
we are headed." Lao Tsu
--

[Moe Meantam]

Post by Chris
Can somebody provide a simple explanation of the difference between a
machine gun (ex .50 or .303 on Allied aircraft) and cannon (ex 20mm on
German a/c).
I used to think cannons shot explosive rounds and guns shot kinetic
energy rounds, but I saw a show on TV comparing .303 to 20mm and the
20mm seemed to be shooting kinetic energy rounds. Also the A10
Warthog has a "cannon" that shoots inert heavy metal rounds. Now I'm
confused.
Is the size of the round the determining factor? Greater than
12mm/.50 cal is a cannon?

This has certainly been an interesting thread, and it is clear that no
consensus has been reached by the participants. I can no longer
resist the temptation to throw my own wrench into the works. :)

According to definitions I have looked up, a cannon is (among other
non-pertinant definitions):

1) A large artillery gun that is usually on wheels.
2) A heavy automatic gun fired from an aircraft.

So, these definitions would appear to clarify the confusion about
smaller caliber weapons being considered cannons when mounted in an
aircraft, and machine-guns when utilized by infantry or armor. I'm
sure that this opinion will not meet with unanimity, but there you
are. Other sites give differing definitions:

1) A cannon is also a modern day rifled machine gun with a calibre of
20mm or more.

The legal definition of "machine-gun" appears to be "Any firearm that
fires more than one bullet at a time with each pull of the trigger."
Thus, a machine-gun that fires heavy caliber shot could also be a
cannon, and a small-caliber aircraft mounted cannon can also be a
machine-gun if it fires multiple rounds. Clear as mud?

--
Al Brennan

"If we do not change direction, we will end up where
we are headed." Lao Tsu
--

[Brian Orion]

Chris,I must have watched the same show and I looked up the terms.
My dictionary says a machine gun fires small-arms rounds(but then a
"50 cal.machine-gun" would be a misnomer?)
Brian

********************
There are three kinds of lies; lies,damned lies,and
statistics.---Disraeli