# Can a 20mm cannon penetrate the sidal armour of an M1 Abrams? And other questions. **URL:** \ **Category:** Factual Questions\ **Created:** [November 1, 2016, 1:22pm UTC](https://boards.straightdope.com/t/can-a-20mm-cannon-penetrate-the-sidal-armour-of-an-m1-abrams-and-other-questions/770358 "2016-11-01T13:22:29Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![DinoR](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dinor/32/2821_2.png) [@DinoR](https://boards.straightdope.com/u/DinoR)\ **Post date:** [November 2, 2016, 6:41pm UTC](https://boards.straightdope.com/t/can-a-20mm-cannon-penetrate-the-sidal-armour-of-an-m1-abrams-and-other-questions/770358/21 "2016-11-02T18:41:11Z")
> [@Gray\_Ghost](#): > > As far as the trebuchet and rock go, don’t tanks often knock down trees while maneuvering in forests? From personal experience, yes. > [@](#): > > Are tanks often damaged by tree tops falling onto their top armor? No. I never saw any damage to the tank from falling trees. If you are doing it right, they mostly don’t fall on you anyway. Hit them slow enough with he center of the front slope and you more push them over/away. It happens though. Especially if things are thick because they can hit trees behind them and bounce back towards you. The tree that landed on my head pulled that deception. Fortunately it didn’t hit me someplace vital. 😃 There was a variety in a few of our training areas that tended to break off higher. The lower trunk on those would push away but the tree tops were like spears of doom hurled straight down onto the top armor by tree gods angry at tanks challenging their supremacy. That didn’t affect the tank either. It WAS scarier. I did, once, mildly bend a couple of the fins on the grill over my exhaust (M1 slick). I did it by ramming into two closely set trees at high speed going backwards. ("Driver hold left!!! _SMASH_ "Driver stop…your other left.) Admittedly one was dead but still standing. That one just exploded into sawdust and splinters. The living tree left chunks we had to pick out and some inconsequential bending to a couple fins. Going forward, taking a tree on the track tended to bend up the fender. It happened more when you were trying to weave in and around the trees to save them. That didn’t affect function. Well the left fender was a nice sleeping spot when I was still on the M60A3; not making a nice bed lumpy is kind of functional. 😛 ---
**Author:** ![muldoonthief](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/muldoonthief/32/3188_2.png) [@muldoonthief](https://boards.straightdope.com/u/muldoonthief)\ **Post date:** [November 2, 2016, 6:41pm UTC](https://boards.straightdope.com/t/can-a-20mm-cannon-penetrate-the-sidal-armour-of-an-m1-abrams-and-other-questions/770358/22 "2016-11-02T18:41:20Z")
> [@GreedySmurf](#): > > The rock would definitely not do any damage to the armour itself. Back of the Envelope calculations only, but the 1.5 ton rock would impact with ~2,000 Kj of kinetic energy. A modern sabot round I believe delivers in excess of 12,000 Kj of kinetic energy. Which depending upon where you hit it, an M1 can shrug off. > > As you suggest, some of the components might suffer, and I suspect a shaken up crew, but good luck hitting a mobile target like a tank with a trebuchet anyway. 😃 You can’t just go by KE though. Dropping a Nimitz class aircraft carrier from a height of 2mm onto an Abrams would also be about 2000 kJ, but I’m guessing the Abrams wouldn’t drive away from it. Even if the rock didn’t penetrate the armor, the momentum of something so large would probably be a mission kill - if it hits the cannon, that’s toast, if it hits the turret, it will probably damage it enough that it couldn’t rotate anymore, would probably destroy any road wheels it hit, etc. I totally agree with the difficulties of hitting a tank from a trebuchet though. ---
**Author:** ![swampspruce](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/swampspruce/32/261_2.png) [@swampspruce](https://boards.straightdope.com/u/swampspruce)\ **Post date:** [November 2, 2016, 10:21pm UTC](https://boards.straightdope.com/t/can-a-20mm-cannon-penetrate-the-sidal-armour-of-an-m1-abrams-and-other-questions/770358/23 "2016-11-02T22:21:52Z")
Defilade the trebuchets and set for a wide dispersion! If we get enough rocks in the air he can’t take us all out… ---
**Author:** ![barath\_s](https://avatars.discourse-cdn.com/v4/letter/b/90ced4/32.png) [@barath\_s](https://boards.straightdope.com/u/barath_s)\ **Post date:** [November 4, 2016, 2:01am UTC](https://boards.straightdope.com/t/can-a-20mm-cannon-penetrate-the-sidal-armour-of-an-m1-abrams-and-other-questions/770358/24 "2016-11-04T02:01:09Z")
> [@carnivorousplant](#): > > What if the trebuchet were on a conveyor belt? What if the trebuchet were on a plane that was on the conveyor belt ---
**Author:** ![Melbourne](https://avatars.discourse-cdn.com/v4/letter/m/b5e925/32.png) [@Melbourne](https://boards.straightdope.com/u/Melbourne)\ **Post date:** [November 4, 2016, 2:50am UTC](https://boards.straightdope.com/t/can-a-20mm-cannon-penetrate-the-sidal-armour-of-an-m1-abrams-and-other-questions/770358/25 "2016-11-04T02:50:44Z")
> [@Banksiaman](#): > > But what if the TANK was thrown by a trebuchet and it flew and tumbled waaaaaaaay away, and landed on its tracks? I don’t fancy the crews’ chances, but could the tank survive that? > > Is the impact of that qualitatively different from a nearby explosion (e.g. neighbouring tank blown up by pouring coke and Mentos down barrel)? > > Straight Dope - tackling the big questions. IN Aus the tank that preceded the Abrams was the Leopard (a German design)… I don’t know anyone who tried the Mentos thing, but I do know that one of the Leopards was disabled by an arrow, shot into the turret bearings. With the barrel stuck out sideways, it’s difficult to manoeuvre through trees ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [November 4, 2016, 11:12am UTC](https://boards.straightdope.com/t/can-a-20mm-cannon-penetrate-the-sidal-armour-of-an-m1-abrams-and-other-questions/770358/26 "2016-11-04T11:12:58Z")
What about reactive armor? As I understand, that works by blowing pieces of itself away. What would it take to trigger the armor to react unnecessarily, and how many hits of that to completely remove the reactive layer? Which would still leave the considerable inert armor underneath, of course, but it might at least leave the tank vulnerable to other weapons. ---
**Author:** ![carnivorousplant](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/carnivorousplant/32/3563_2.png) [@carnivorousplant](https://boards.straightdope.com/u/carnivorousplant)\ **Post date:** [November 4, 2016, 12:39pm UTC](https://boards.straightdope.com/t/can-a-20mm-cannon-penetrate-the-sidal-armour-of-an-m1-abrams-and-other-questions/770358/27 "2016-11-04T12:39:01Z")
> [@barath\_s](#): > > What if the trebuchet were on a plane that was on the conveyor belt A plane with snakes aboard! ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [November 4, 2016, 1:09pm UTC](https://boards.straightdope.com/t/can-a-20mm-cannon-penetrate-the-sidal-armour-of-an-m1-abrams-and-other-questions/770358/28 "2016-11-04T13:09:37Z")
Somewhat related previous thread: [Minimum weapon to damage an Abrams tank?](http://boards.straightdope.com/sdmb/showthread.php?t=599220) ---
**Author:** ![Whiskey\_Dickens](https://avatars.discourse-cdn.com/v4/letter/w/9fc348/32.png) [@Whiskey\_Dickens](https://boards.straightdope.com/u/Whiskey_Dickens)\ **Post date:** [November 4, 2016, 1:23pm UTC](https://boards.straightdope.com/t/can-a-20mm-cannon-penetrate-the-sidal-armour-of-an-m1-abrams-and-other-questions/770358/29 "2016-11-04T13:23:02Z")
Great responses, **DinoR** , **Gray Ghost** and **Corry El**! Always love unca Dino’s Abrams storytime. Keep 'em coming! ---
**Author:** ![Jophiel](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jophiel/32/66_2.png) [@Jophiel](https://boards.straightdope.com/u/Jophiel)\ **Post date:** [November 4, 2016, 1:44pm UTC](https://boards.straightdope.com/t/can-a-20mm-cannon-penetrate-the-sidal-armour-of-an-m1-abrams-and-other-questions/770358/30 "2016-11-04T13:44:27Z")
I don’t have an answer for the OP but on November 1st I was ALSO Googling whether or not a tank could be taken out with a catapult about an hour before this post came up. Which makes me wonder what was going on Nov 1st to put that thought into both our heads. ---
**Author:** ![DesertDog](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/desertdog/32/11503_2.png) [@DesertDog](https://boards.straightdope.com/u/DesertDog)\ **Post date:** [November 4, 2016, 2:00pm UTC](https://boards.straightdope.com/t/can-a-20mm-cannon-penetrate-the-sidal-armour-of-an-m1-abrams-and-other-questions/770358/31 "2016-11-04T14:00:57Z")
> [@snfaulkner](#): > > I’m trying to imagine a trebuchet capable of throwing a 60+ ton projectile waaaaaaaay away. Truly. Last year the Department of Public Works at Burning Man fired a [flaming piano](https://www.youtube.com/watch?v=6Rn8jBzsg9U)\* from a treb and the distance was . . . unimpressive. \*Not really shown in the video is the squad jumping on the debris to clean up the mess; it took them seven minutes. ---
**Author:** ![Channing\_Idaho\_Banks](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/channing_idaho_banks/32/250_2.png) [@Channing\_Idaho\_Banks](https://boards.straightdope.com/u/Channing_Idaho_Banks)\ **Post date:** [November 4, 2016, 2:11pm UTC](https://boards.straightdope.com/t/can-a-20mm-cannon-penetrate-the-sidal-armour-of-an-m1-abrams-and-other-questions/770358/32 "2016-11-04T14:11:50Z")
Do tanks actually use sidal armor or is the OP just making that up? ---
**Author:** ![bump](https://avatars.discourse-cdn.com/v4/letter/b/7c8e57/32.png) [@bump](https://boards.straightdope.com/u/bump)\ **Post date:** [November 4, 2016, 2:22pm UTC](https://boards.straightdope.com/t/can-a-20mm-cannon-penetrate-the-sidal-armour-of-an-m1-abrams-and-other-questions/770358/33 "2016-11-04T14:22:35Z")
> [@muldoonthief](#): > > You can’t just go by KE though. Dropping a Nimitz class aircraft carrier from a height of 2mm onto an Abrams would also be about 2000 kJ, but I’m guessing the Abrams wouldn’t drive away from it. > > Even if the rock didn’t penetrate the armor, the momentum of something so large would probably be a mission kill - if it hits the cannon, that’s toast, if it hits the turret, it will probably damage it enough that it couldn’t rotate anymore, would probably destroy any road wheels it hit, etc. Sure, but the crews are what count; all the tanks, airplanes, etc… in the world don’t matter if you don’t have trained crews to put in them. ---
**Author:** ![Enilno](https://avatars.discourse-cdn.com/v4/letter/e/58f4c7/32.png) [@Enilno](https://boards.straightdope.com/u/Enilno)\ **Post date:** [November 4, 2016, 2:49pm UTC](https://boards.straightdope.com/t/can-a-20mm-cannon-penetrate-the-sidal-armour-of-an-m1-abrams-and-other-questions/770358/34 "2016-11-04T14:49:15Z")
If I can approach the question from the other direction, how fast would a round from say, the M61 Vulcan, which wiki says weighs 102.4 g, have to be traveling to be able to defeat the armor. I assume if you can put enough kinetic energy into the round that at some point it’ll be enough. ---
**Author:** ![Mr\_Quatro](https://avatars.discourse-cdn.com/v4/letter/m/bc8723/32.png) [@Mr\_Quatro](https://boards.straightdope.com/u/Mr_Quatro)\ **Post date:** [November 4, 2016, 3:08pm UTC](https://boards.straightdope.com/t/can-a-20mm-cannon-penetrate-the-sidal-armour-of-an-m1-abrams-and-other-questions/770358/35 "2016-11-04T15:08:52Z")
Does the tank in question have electronics on board? It’s just a matter of time before they invent a hand held EMP rifle. This article is only two (2) weeks old: > **[Raytheon EMP weapon tested by Boeing, USAF Research Lab - Military Embedded...](https://militaryembedded.com/radar-ew/sensors/raytheon-emp-missile-tested-by-boeing-usaf-research-lab)** > > Boeing has announced that it successfully tested an electromagnetic pulse missile capable of disabling electronics without affecting structures. The Counter-electronics High-powered Advanced Missile Project (CHAMP) was tested by a Boeing Phantom... > [@](#): > > Boeing has announced that it successfully tested an electromagnetic pulse missile capable of disabling electronics without affecting structures. The Counter-electronics High-powered Advanced Missile Project (CHAMP) was tested by a Boeing Phantom Works/U.S. Air Force Research Laboratory Directed Energy Directorate team on October 16 at the Utah Test and Training Range. ---
**Author:** ![muldoonthief](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/muldoonthief/32/3188_2.png) [@muldoonthief](https://boards.straightdope.com/u/muldoonthief)\ **Post date:** [November 4, 2016, 4:50pm UTC](https://boards.straightdope.com/t/can-a-20mm-cannon-penetrate-the-sidal-armour-of-an-m1-abrams-and-other-questions/770358/36 "2016-11-04T16:50:46Z")
> [@bump](#): > > Sure, but the crews are what count; all the tanks, airplanes, etc… in the world don’t matter if you don’t have trained crews to put in them. In the long run, sure. But in the middle of a battle, rendering an enemy tank unusable is good enough for now. ---
**Author:** ![Gunslinger](https://avatars.discourse-cdn.com/v4/letter/g/4491bb/32.png) [@Gunslinger](https://boards.straightdope.com/u/Gunslinger)\ **Post date:** [November 5, 2016, 12:32am UTC](https://boards.straightdope.com/t/can-a-20mm-cannon-penetrate-the-sidal-armour-of-an-m1-abrams-and-other-questions/770358/37 "2016-11-05T00:32:27Z")
Remember, though, the armor’s thinnest on the top, so a sufficiently big artillery shell (or trebuchet-flung rock) will splat a tank like a bug. But if the rock hits the side (good luck aiming a trebuchet at a fast-moving vehicle, though) and knocks off a track, well, now it’s a pillbox that still has 3-4 heavy machine guns (with longer range than the trebuchet) and one REALLY BIG gun (and probably at least several rounds each of HE and [canister,](http://www.gd-ots.com/LCA_120mm_M1028.html) in addition to the lawn darts). And they’re going to be \*\*extremely angry \*\*at the trebuchet crew. Better hope the second rock-flinger in the battery has better aim. Tangent: > [@muldoonthief](#): > > In the long run, sure. But in the middle of a battle, rendering an enemy tank unusable is good enough for now. Yeah, but not all that great if they get it back and fix it (or the crew bailed, and climb back in once you move on to find the interior damage isn’t as bad as they thought/hose out what’s left of the driver) and continue on as soon as you drive away. There’s a reason one of the big rules of antitank gunnery has traditionally been “keep shooting it until it burns or explodes.” Especially if there’s a chance you may not end up holding the ground at the end of the day. There was one M1 temporarily knocked out during Desert Storm (penetrating hit of “unknown origin\*” killed or seriously injured the driver, IIRC, but no major damage to the tank itself aside from a hole in it). They sent the casualty back to collect his Purple Heart and kept going for two or three weeks with just three crewmen, until somebody happened to walk by the tank with a Geiger counter and realize it was hot as hell, and not in the sun-baked sense. :eek: Turns out, \*whatever \*had hit it had filled it with mildly radioactive dust. Fun fact: tank crewmen start as a driver, then train to become a loader, loader trains on how to work the gun, gunner learns to be a commander as they advance up the ranks, that way if somebody gets knocked out, the next guy up can cover his position, the guy above that covers that guy’s, and the commander does double duty as gunner. (And I guess if the CDR gets whacked the gunner gets a promotion.) (\*-- i.e., they never found out which of its platoonmates the shot came from; there’s not much that’ll get through the front of an Abrams, and only one thing that’s radioactive) ---
**Author:** ![Precambrianmollusc](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/precambrianmollusc/32/63_2.png) [@Precambrianmollusc](https://boards.straightdope.com/u/Precambrianmollusc)\ **Post date:** [November 6, 2016, 2:02am UTC](https://boards.straightdope.com/t/can-a-20mm-cannon-penetrate-the-sidal-armour-of-an-m1-abrams-and-other-questions/770358/38 "2016-11-06T02:02:36Z")
> [@GreedySmurf](#): > > T > > As you suggest, some of the components might suffer, and I suspect a shaken up crew, but good luck hitting a mobile target like a tank with a trebuchet anyway. 😃 But if the tank is on a treadmill? . ---
**Author:** ![Precambrianmollusc](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/precambrianmollusc/32/63_2.png) [@Precambrianmollusc](https://boards.straightdope.com/u/Precambrianmollusc)\ **Post date:** [November 6, 2016, 2:22am UTC](https://boards.straightdope.com/t/can-a-20mm-cannon-penetrate-the-sidal-armour-of-an-m1-abrams-and-other-questions/770358/39 "2016-11-06T02:22:51Z")
> [@Gunslinger](#): > > Remember, though, the armor’s thinnest on the top, so a sufficiently big artillery shell (or trebuchet-flung rock) will splat a tank like a bug. The question here though is ‘what is sufficiently big?’ . Clearly by definition anything that is ‘sufficiently big’ will do what it is sufficient for . . ---
**Author:** ![drachillix](https://avatars.discourse-cdn.com/v4/letter/d/48db29/32.png) [@drachillix](https://boards.straightdope.com/u/drachillix)\ **Post date:** [November 6, 2016, 3:56am UTC](https://boards.straightdope.com/t/can-a-20mm-cannon-penetrate-the-sidal-armour-of-an-m1-abrams-and-other-questions/770358/40 "2016-11-06T03:56:39Z")
> [@barath\_s](#): > > What if the trebuchet were on a plane that was on the conveyor belt The rock flies [Previous page](https://boards.straightdope.com/t/can-a-20mm-cannon-penetrate-the-sidal-armour-of-an-m1-abrams-and-other-questions/770358.md?page=1) [Next page](https://boards.straightdope.com/t/can-a-20mm-cannon-penetrate-the-sidal-armour-of-an-m1-abrams-and-other-questions/770358.md?page=3)