# Is anything over 15mm considered a cannon shell by the U.S. military? **URL:** \ **Category:** Factual Questions\ **Created:** [September 27, 2013, 11:19pm UTC](https://boards.straightdope.com/t/is-anything-over-15mm-considered-a-cannon-shell-by-the-u-s-military/669844 "2013-09-27T23:19:02Z")\ **Posts on this page:** 15\ **Page:** 1
**Author:** ![SeaCanary](https://avatars.discourse-cdn.com/v4/letter/s/e274bd/32.png) [@SeaCanary](https://boards.straightdope.com/u/SeaCanary)\ **Post date:** [September 27, 2013, 11:19pm UTC](https://boards.straightdope.com/t/is-anything-over-15mm-considered-a-cannon-shell-by-the-u-s-military/669844/1 "2013-09-27T23:19:02Z")
I.e., .50 caliber is not a cannon shell and 20mm is a cannon shell. ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [September 28, 2013, 12:43am UTC](https://boards.straightdope.com/t/is-anything-over-15mm-considered-a-cannon-shell-by-the-u-s-military/669844/2 "2013-09-28T00:43:18Z")
Do we still call them “cannons?” I thought they had specific names like Howitzer, Recoilless Rifle, Anti-Tank gun, etc. If a Colonel in battle shouted, bring up the cannon, would people look at him funny? ---
**Author:** ![aNewLeaf](https://avatars.discourse-cdn.com/v4/letter/a/ac91a4/32.png) [@aNewLeaf](https://boards.straightdope.com/u/aNewLeaf)\ **Post date:** [September 28, 2013, 12:48am UTC](https://boards.straightdope.com/t/is-anything-over-15mm-considered-a-cannon-shell-by-the-u-s-military/669844/3 "2013-09-28T00:48:20Z")
Cannon isn’t a term. “Guns” are based on caliber, a howitzer is a gun while an M16 is not (it’s a rifle or weapon). ---
**Author:** ![JRDelirious](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jrdelirious/32/9531_2.png) [@JRDelirious](https://boards.straightdope.com/u/JRDelirious)\ **Post date:** [September 28, 2013, 3:26am UTC](https://boards.straightdope.com/t/is-anything-over-15mm-considered-a-cannon-shell-by-the-u-s-military/669844/4 "2013-09-28T03:26:28Z")
[This is called a cannon](http://en.wikipedia.org/wiki/M61_Vulcan) So’s[this](http://en.wikipedia.org/wiki/GAU-12_Equalizer). Commonly when mounted on aircraft. Similarly the [20mm Oerlikon](http://en.wikipedia.org/wiki/20mm_Oerlikon)AA piece of WW2 fame and still kicking around. And sometimes [this thing as well](http://en.wikipedia.org/wiki/M242_Bushmaster). ---
**Author:** ![Ranger\_Jeff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ranger_jeff/32/2065_2.png) [@Ranger\_Jeff](https://boards.straightdope.com/u/Ranger_Jeff)\ **Post date:** [September 28, 2013, 6:15am UTC](https://boards.straightdope.com/t/is-anything-over-15mm-considered-a-cannon-shell-by-the-u-s-military/669844/5 "2013-09-28T06:15:02Z")
> [@Trinopus](#): > > Do we still call them “cannons?” I thought they had specific names like Howitzer, Recoilless Rifle, Anti-Tank gun, etc. If a Colonel in battle shouted, bring up the cannon, would people look at him funny? At one time, cannons were for direct fire and howitzers were for indirect fire. I seem to recall reading somewhere that if the tube can be elevated more than 35°, it’s a howitzer. And nowadays, the Colonel would radio the artillery battery and request a fire mission. ---
**Author:** ![Koxinga](https://avatars.discourse-cdn.com/v4/letter/k/4af34b/32.png) [@Koxinga](https://boards.straightdope.com/u/Koxinga)\ **Post date:** [September 28, 2013, 7:37am UTC](https://boards.straightdope.com/t/is-anything-over-15mm-considered-a-cannon-shell-by-the-u-s-military/669844/6 "2013-09-28T07:37:03Z")
Is it for fighting or is it for fun? ---
**Author:** ![SeaCanary](https://avatars.discourse-cdn.com/v4/letter/s/e274bd/32.png) [@SeaCanary](https://boards.straightdope.com/u/SeaCanary)\ **Post date:** [September 28, 2013, 3:48pm UTC](https://boards.straightdope.com/t/is-anything-over-15mm-considered-a-cannon-shell-by-the-u-s-military/669844/7 "2013-09-28T15:48:11Z")
I will rephrase: Is anything over 15mm considered to be either a cannon or artillery shell by the U.S. military? 🙂 ---
**Author:** ![Dissonance](https://avatars.discourse-cdn.com/v4/letter/d/85f322/32.png) [@Dissonance](https://boards.straightdope.com/u/Dissonance)\ **Post date:** [September 28, 2013, 5:10pm UTC](https://boards.straightdope.com/t/is-anything-over-15mm-considered-a-cannon-shell-by-the-u-s-military/669844/8 "2013-09-28T17:10:57Z")
I’m unaware if there is an official ruling by the US military on it, but yes, the general rule is anything greater than 15mm is a cannon shell; 12.7mm-14.5mm are heavy machine guns firing bullets, and anything below 12.7mm is a general purpose, medium or light machine gun or small arm again firing bullets. 15mm isn’t a widely used caliber; things usually jump from 12.7mm (the US M2HB HMG) or 14.5mm (the former Soviet [KPV](http://en.wikipedia.org/wiki/KPV_heavy_machine_gun) HMG) straight to 20mm or greater. [Cite](http://en.wikipedia.org/wiki/Heavy_machine_gun): > [@](#): > > Currently, firearms with calibers smaller than 12.7 mm are generally considered medium or light machine guns, while those larger than 15.24 mm are generally classified as autocannons instead of heavy machine guns. [Cite](http://en.wikipedia.org/wiki/Autocannon): > [@](#): > > An autocannon or automatic cannon is a rapid-fire projectile weapon that fires armour piercing or explosive shells, as opposed to the bullet fired by a machine gun. Autocannons often have a larger calibre than a machine gun (e.g., 20 mm or greater). Usually, autocannons are smaller than a field gun or other artillery, and are mechanically loaded for a faster rate of fire. ---
**Author:** ![RickJay](https://avatars.discourse-cdn.com/v4/letter/r/bb73d2/32.png) [@RickJay](https://boards.straightdope.com/u/RickJay)\ **Post date:** [September 28, 2013, 6:15pm UTC](https://boards.straightdope.com/t/is-anything-over-15mm-considered-a-cannon-shell-by-the-u-s-military/669844/9 "2013-09-28T18:15:08Z")
> [@SeaCanary](#): > > I will rephrase: Is anything over 15mm considered to be either a cannon or artillery shell by the U.S. military? 🙂 The really factual answer to your question is that there is no precise definition of what is a “cannon,” and something that is a “cannon” can fire things that are sometimes called “shells” and sometimes not. Is the 120mm weapon on an M1 tank a cannon or a gun? There’s no real definition. Does it fire shells? Well, sometimes. But sometimes it fires sabot rounds, and it can also fire the LAHAT missile although I don’t know if the US Army has purchased any yet. Common military terms often don’t have clearly defined lines. What’s the difference between a frigate, a destroyer, and a cruiser? There isn’t a clear difference. ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [September 28, 2013, 8:09pm UTC](https://boards.straightdope.com/t/is-anything-over-15mm-considered-a-cannon-shell-by-the-u-s-military/669844/10 "2013-09-28T20:09:34Z")
Could you make a rough discrimination on the basis of explosive shells vs. inert shells? Pistols, rifles, and machine-guns fire inert rounds. (Slugs, so to speak.) The big stuff sends a package of explosive goodness to the enemy. (Oops, except for the very basic solid-round anti-tank shell… Do we still use those at all?) ---
**Author:** ![Ranger\_Jeff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ranger_jeff/32/2065_2.png) [@Ranger\_Jeff](https://boards.straightdope.com/u/Ranger_Jeff)\ **Post date:** [September 28, 2013, 9:25pm UTC](https://boards.straightdope.com/t/is-anything-over-15mm-considered-a-cannon-shell-by-the-u-s-military/669844/11 "2013-09-28T21:25:49Z")
I was informed that a “gun” is a crew served weapon. So, “gun” would be a not quite all inclusive term describing machine guns, cannons, mortars, howitzers, recoiless rifles, etc. ---
**Author:** ![Ranger\_Jeff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/ranger_jeff/32/2065_2.png) [@Ranger\_Jeff](https://boards.straightdope.com/u/Ranger_Jeff)\ **Post date:** [September 28, 2013, 9:27pm UTC](https://boards.straightdope.com/t/is-anything-over-15mm-considered-a-cannon-shell-by-the-u-s-military/669844/12 "2013-09-28T21:27:16Z")
> [@Trinopus](#): > > Could you make a rough discrimination on the basis of explosive shells vs. inert shells? Pistols, rifles, and machine-guns fire inert rounds. (Slugs, so to speak.) The big stuff sends a package of explosive goodness to the enemy. > > (Oops, except for the very basic solid-round anti-tank shell… Do we still use those at all?) Yes. They’re often made of depleted uranium, are fin guided, and have a discarding sabot. ---
**Author:** ![ExTank](https://avatars.discourse-cdn.com/v4/letter/e/35a633/32.png) [@ExTank](https://boards.straightdope.com/u/ExTank)\ **Post date:** [September 28, 2013, 9:38pm UTC](https://boards.straightdope.com/t/is-anything-over-15mm-considered-a-cannon-shell-by-the-u-s-military/669844/13 "2013-09-28T21:38:21Z")
> [@Trinopus](#): > > (Oops, except for the very basic solid-round anti-tank shell… Do we still use those at all?) [Meet the M829-series “Silver Bullet” APFSDS-DU.](http://en.wikipedia.org/wiki/M829_(munition)) It’s a tank killer. ---
**Author:** ![Gagundathar](https://avatars.discourse-cdn.com/v4/letter/g/a183cd/32.png) [@Gagundathar](https://boards.straightdope.com/u/Gagundathar)\ **Post date:** [September 28, 2013, 9:47pm UTC](https://boards.straightdope.com/t/is-anything-over-15mm-considered-a-cannon-shell-by-the-u-s-military/669844/14 "2013-09-28T21:47:26Z")
I find it remarkable that even now in this technologically based society, we still have such imprecise terms for objects. There is no universal standard for what is a cannon shell vs. bullet, or a mountain vs. a hill or a ship vs. a boat. Some see this as a bug and others as a feature. I wonder if other languages have similar characteristics of vagueness. ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [September 28, 2013, 11:33pm UTC](https://boards.straightdope.com/t/is-anything-over-15mm-considered-a-cannon-shell-by-the-u-s-military/669844/15 "2013-09-28T23:33:06Z")
> [@Ranger\_Jeff](#): > > Yes. They’re often made of depleted uranium, are fin guided, and have a discarding sabot. > [@ExTank](#): > > [Meet the M829-series “Silver Bullet” APFSDS-DU.](http://en.wikipedia.org/wiki/M829_(munition)) It’s a tank killer. Cool to know! I remember when HEAT rounds were new (not to mention HESH!) so I had wondered if the old style was still used. (Adding fins and a drop sabot makes it all new again!) Thank you! (Why, yes, I do use too many exclamation points!)