Whats the difference between a Machine gun and a cannon ?

I wasnt sure if this was supposed to go into guns galore or members lounge. But anyways.

My questions is: whats the difference between a cannon and a machine gun ?

 

All cannons can be called guns, but not all guns can be called cannons. It is a difference in calibre - AFAIK, from 20 mm and up is cannon, while a heavy MG would be 12.7 mm.

That is what I think, at least... we'll see soon if it is right or wrong!

 

Living dangerously amongst all the expertise here, but AFAIK a "cannon" (at least in aircraft armament terms) fires explosive shells while an MG fires non-explosive bullets. OK, incendaries and tracer blur things somewhat....


Tom

 

I think MG refers to any rapid firing, autoloading, rifle caliber or larger (but less than 20MM) weapon that does not fire explosive rounds.
Cannon is a somewhat antiquated term that has held over from earlier days and refers AFAIK to 20mm or larger weapons that may or may not fire an explosive round and may or may not be autoloaders.
Clear as mud?

 

When I had the preview of the military chanal that is the same thing that they said, and what I think the difference is so I ahve to assume you are right.

 

I think Grieg is right.

 

euhm, for what does AFAIK stand for??

 

As Far As I Know

 

The definition seems a bit blurred and can change, I understood it to be 15mm and greater was a cannon less than 15mm was a machinegun.

The logic behind this was that 15mm was reckoned to be the smallest sized round that could contain a practical explosive charge, it was possible in smaller rounds but not generally considered worth the effort.

I understand though that it is now generally accepted that the cut-off is 20mm, not that it makes a huge amount of difference really, I can only think of one cannon that would be reclassified as a machinegun (The Mg151) in this instance.

To muddy things slightly further, as Tony Williams once pointed out, the Luftwaffe apparently considered even 20mm to be a machinegun as they gave their wartime 20mm cannon "MG" designations.

That aside, either 15mm or 20mm is the cut-off point, take your pick, although 20mm seems to be the more widely accepted one.

 

From my book Rapid Fire: the Development of Automatic Cannon, Heavy Machine Guns and their Ammunition for Armies, Navies and Air Forces:

"This book is concerned with heavy machine guns (HMGs) and automatic cannon. The current usage of these terms has only become generally accepted since the Second World War. Before then, the term "machine gun" was used to describe a relatively small-calibre weapon normally firing solid projectiles while larger weapons were called "automatic guns". The name "cannon" was in English usage an obsolete term for artillery, which by that time were known as guns or howitzers depending on their function. The situation changed in British practice with the selection for the RAF of the French Hispano moteur-canon in the late 1930s. Anglicised as "cannon", the name became adopted for the Hispano and subsequently for all other automatic shell-firing guns of 20mm or more calibre.

Different nations had different practices; in Germany, automatic weapons of up to and including 20mm were known as machine guns (Maschinengewehr) with larger calibres being known as cannon (Maschinenkanonen), leading to the MG and MK prefixes....

Nomenclature also varied between services. In Sweden, the Air Force called their m/39 12.7mm and 13.2mm guns automatkanon, presumably because they were larger than usual for aircraft guns at the time, while their Navy called the m/32 25mm a kulspruta, (which translates as machine gun), presumably because this was a small weapon by naval standards.

Since the war the definition of a cannon as any fast-firing automatic weapon of 20mm or more has become generally accepted, at least in NATO. The term heavy machine gun has also seen some changes. At one time it was literally used to describe a gun which weighed a lot, of the sturdily-built sort which might be used to defend fortifications, even if it was of rifle calibre. Such weapons have long gone, however, all current rifle calibre machine guns (RCMGs) being relatively light by previous standards, so the term HMG has come to be used for a class of weapon which fits in between RCMGs and cannon. By some form of convergent evolution, the calibre of virtually all HMGs to see service has fallen within the range 12.7-15mm."

While it is generally true that cannon fire explosive shells while MGs fire solid bullets there have been many exceptions to this, especially in aircraft gun ammo where even rifle-calibre HE bullets have been used.

Tony Williams: Military gun and ammunition website and discussion forum

 

thanks tony, and everyone else that contributed.

 

Tony, you beat me to it. I thought I was going to be able to use some of that knowledge I learned from reading your book. Thanks a lot! :lol: