What's the difference between a rifle (or gun) and a cannon?

Title pretty much says it all but for some examples:

You hear of the big guns on a battleship referred to as a naval rifle.

Tanks are described as using cannons…not rifles.

The F86 Sabre aircraft used a 20mm cannon. Its rival, the MiG-15 in some variants used a 12.7mm machine gun.

How is the distinction drawn between cannons and guns (or rifles)?

I thought a rifle (of any size) had spiral slots or indentations or something inside the barrel to cause the shell/bullet to spin in flight and fly straighter and more accurately, while a cannon or gun (of any size)… didn’t. I could be very wrong on this.

I was thinking about that but some tanks have a rifled barrel (although I think modern tanks use a smoothbore gun…could be wrong).

Yeah, basically a rifle is any firearm that has spiral grooves in the inside of the barrel (cleverly refered to as… rifling) which make the bullet spin like a football, improving accuracy at long range.

The reasoning that was explained to me for the differences between cannons and machine guns on fighters in the 40’s and 50’s was that a cannon fired explosive rounds, though in modern examples (such as the 20mm Vulcan canon used by American fighter planes) the cannons are externally powered, instead of gas-powered, so they wouldn’t be considered a machine gun no matter what kind of bullets they spat out.

American tanks (and I think German ones too, dunno about anyone else) use Smoothbore cannons… no rifling. Hence, they’re not rifles regardless of what else they’re called. I think “Cannon” is just the catch-all phrase for “A firearm that fires really really big bullets”.

Interestingly enough, most modern handguns (such as the Beretta 92) are also Rifles, due to the rifling used in their barrels, though in regards to hand-held firearms, it seems that the gun needs to be of a certain length to be considered a Rifle (Make it a bit shorter, it becomes a Carbine, remove the stock, it becomes a Pistol) “Gun” is a sort of catch-all phrase for any kind of firearm, as well as Air-guns (Think a regular gun, but it uses compressed air instead of exploding gasses to propel the bullet)

Also, in regards to the Sabre, early versions had six .50 calibre machine guns mounted in the nose.

Rifle definately refers to the spiral grooves cut into the barrel. So a weapon can be both a rifle and a cannon. But not all cannons are rifles (The M-1 tank uses a smoothbore cannon. The round has fins to impart spin instead of rifling in the barrel). Likewise, not all rifles are cannons. Anyone who uses a hunting rifle can tell you that.

20mm seems to be the arbitrary point at which a weapon is called a cannon. I don’t know if there is a technical difference or if everyone simply agreed on it for classification purposes.

Man, I’ve got to be quicker if I want to be first on this board.

I remember this from a “UK vs US” thread, the Abhrams tank uses a smoothbore cannon and the British Challenger uses a rifled cannon, so the Abhrams packs more of a punch.

And on a related note, what’s the difference between a chain-gun and a machine gun, as found on the Challenger tank.

A machine gun is operated by the gunpowder in the bullets, either through the recoil of the shell, or the expanding gasses going down the barrel. A chain gun is externally powered by an electric motor. One difference this makes is that a dud round will stop a machine gun until the gunner clears the gun and pulls the trigger again. The chain gun will simply eject the dud round and keep going without interruption. Another difference is that chain guns can have a much higher rate of fire than a MG. MGs can still get up there. The german MG42 fired 1,200 rounds a minute. But a chaingun can pump out 3,000 RPM.

I’ve never heard reference to a chain gun outside of a video game but Hypno-Toad’s description of a rotary gun is right on. They are often called Gatling guns but that term is only correctly applied to the Civil war era hand cranked version. Not all actually eject rounds. The M-61 gun used in many US military planes has a continuous feed belt that sends rounds back into the drum, fired or not. This allows the belt and rotary barrels to come up to speed, fire a specified burst and come to a stop without throwing good rounds away. When all the usable rounds are fired the belt in the drum has alternating stretches of fired and live rounds that can be recovered when it is reloaded.

Nitpick: The M1 uses a rifled 105 mm cannon. The M1A1 and M1A2 use a German 120 mm smooth bore cannon (designated M256 by the US DOD).

Larger rifled guns have been designated as rifles, possibly to clear things up in the supply chain. I’d assume that a 16" rifle used different shells than a 16" smoothbore cannon.

Hmm… I assumed that all the original M1s had been refit to M1A1 or M1A2 standards. So if I was correct in that assumption, then the M1s used a rifled cannon, but use a smoothbore now.

Was my assumption incorrectly made? If so, then on behalf of me I’d like to say “Oops.”

saying ‘cannon’ about an artillery piece is like calling the Queen Mary a boat - here, anyway. ‘Cannon’ gets reserved for aircraft (or light armoured vehicle) guns of 30mm or less with explosive projectiles.
Naval ‘rifle’ probably dates from the transitional period in the 19th c. when naval artillery was a mixture of rifled and smoothbored guns

"This is my rifle and
this is my gun"

[sup]Said gun definitely has a smooth bore.[/sup]

No wonder I can never get long range accuracy.

Remember, it’s not the muzzle velocity that counts, it’s the trajectory of the shot.

It all gets confusing and I’m not totally straight on all of it.

A cannon is the generic term for a large gun. How large? Well, some of them are refrerred to as 20 mm (0.787 in.) cannons.

In the artillery the term gun is often used to distinguish a relatively long barreled piece from a howitzer which is a cannon with a big bore and a short barrel useful for high angle, plunging fire.

A piece with a short barrel and a big bore intended to deliver plunging fire is also sometimes called a mortar.

A naval rifle is a cannon with a caliber of more than, say, 30. This means that the barrel length is 30 times the bore diameter. Most naval rifles are around 50 caliber.

Caliber also can refer to the diameter of the bore in small arms. Such as a 30 caliber hunting rifle.

These terms are all used, are historical and have grown up over a long period of time.

Well, glad we got that all cleared up.

Yeah. That’s what you get for letting the hoi poloi do their own naming.

Earlier related topic thread:

Cannon or Gun?

[ nitpick ]

This sentence is misleading. The machine gun that the article mentions was mounted on a trainer. The actual combat MiGs were armed (as noted on the page) with a pair of 23mm cannon plus a 37mm cannon that combined to tear the hell out of anything that got in its sights. The F-86 was actually under-armed (until later models) with six .50 caliber (or 12.7mm) machine guns, which made killing the heavily armored MiG a hassle throughout the Korean war. (Interestingly, the Navy version, the FJ Fury, was armed with four 20mm cannon from the outset.)

[ /nitpick ]

The nomenclature “12.7mm machine gun” was simply the European mode of identifying the same bore diameter as the .50 caliber expression used by the U.S. Similarly, American weapons identified as .30 caliber were generally identified in Europe as 7.62 mm.