dennett@Kodak.COM (Charlie Dennett) (08/30/90)
From: dennett@Kodak.COM (Charlie Dennett) Sorry if this is an often asked or otherwise dumb question. I've only read this group off and on for the last few months. Just what is the difference between a cannon and a machine gun (at least as it applies to planes?) Does a cannon have a smooth bore and a mg have a rifled bore? Does a cannon also have an explosive projectile? Thanks for putting up with me. :-) Charlie Dennett | Internet: dennett@Kodak.COM Mail Stop 01816 | Phone: (716) 588-6078 Eastman Kodak Company | -- This space under construction -- Rochester, NY 14650-1816 | -- Be prepared to stop --
henry@zoo.toronto.edu (Henry Spencer) (09/02/90)
From: henry@zoo.toronto.edu (Henry Spencer) >From: dennett@Kodak.COM (Charlie Dennett) >Just what is the difference between a cannon and a machine gun (at least >as it applies to planes?) Does a cannon have a smooth bore and a mg >have a rifled bore? Does a cannon also have an explosive projectile? I think the distinction was originally based on the ability to fire an explosive shell. There is otherwise no sharp boundary: both have rifled barrels, they often have similar mechanisms, rates of fire vary widely (for example, the 20mm Vulcan cannon has a higher rate of fire than any conventional MG), and muzzle velocities are not a reliable guide. In fact, it's more a matter of tradition than anything else. As I recall, the 20mm explosive cannon shell carries such a puny charge that it's not often used, while the .50cal incendiary MG bullet is said to be very good at killing aircraft. Actually, there is a noticeable tendency in recent years to move away from the borderline in any case. Infantry and related weapons are moving to smaller calibers, given the advantages of lighter ammunition and the extreme rarity of long-range rifle/MG engagements; even 7.62mm is now considered a rather large caliber. Aircraft and antiaircraft weapons, on the other hand, are growing away from the 20mm cannon, now considered a bit small, towards 30-35mm, where explosive shells are really useful. Actually, the 20mm cannon would probably be extinct in such applications were it not that the US has so far been unsuccessful at developing a bigger air-to-air gun for its aircraft. Everyone else went to bigger calibers long ago; about the smallest in use elsewhere is the Tornado's 27mm Mauser, and probably the best is Oerlikon's 30mm KCA. Henry Spencer at U of Toronto Zoology henry@zoo.toronto.edu utzoo!henry
bxr307@csc.anu.oz (09/02/90)
From: bxr307@csc.anu.oz In article <1990Aug30.030107.29349@cbnews.att.com>, dennett@Kodak.COM (Charlie Dennett) writes: > > > From: dennett@Kodak.COM (Charlie Dennett) > Sorry if this is an often asked or otherwise dumb question. I've only read > this group off and on for the last few months. > > Just what is the difference between a cannon and a machine gun (at least > as it applies to planes?) Does a cannon have a smooth bore and a mg > have a rifled bore? Does a cannon also have an explosive projectile? The old classic definition was that anything below 15mm in calibre was classed as a machine gun and anything above a cannon (regardless of whether it fired an explosive round or not). However with the introduction of the Soviet 14.5mm HMG that definition has become rather blurred. The 14.5mm fires a HE round but is classed as a HMG. However by simply changing the definition to differentiate between weapons which fire explosive versus solid rounds would have trouble explaining the various small calibre cannon of 20-40mm which now fire APDS/APFSDS/AP round which are all non-explosive in nature. So it can be seen that it is difficult to decide what is a cannon and what is a machine gun. However I think the easiest way would be to simply have a definition which depended not on the calibre of the weapon, or even on what round it fires, rather the type of round which it fires most of the time. Therefore a 14.5mm HMG would be simply that, a HMG as it fires for most of the time normal ball ammunition. Whereas the 20-40mm cannons are cannons because they fire a mix of HE/AP rounds usually with the HE predominating for most missions (except in anti-armour). Both MG's and Cannons rely, at the moment on rifling in their barrels to impart spin to their rounds. However with the advent of APFSDS rounds for 30-40mm calibre guns promising quite good penetration I somehow think that the rifling will soon be considered superflous for these weapons, just as it is now for most tank guns (I wonder why the Brits are still sticking with a rifled barrel for the 120mm? Perhaps they know something other countries have ignored? ;-) Brian Ross