# Rifling on Battle Tank Main Armament **URL:** \ **Category:** Factual Questions\ **Created:** [August 5, 2010, 5:58pm UTC](https://boards.straightdope.com/t/rifling-on-battle-tank-main-armament/549303 "2010-08-05T17:58:23Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![smithsb](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/smithsb/32/12107_2.png) [@smithsb](https://boards.straightdope.com/u/smithsb)\ **Post date:** [August 6, 2010, 4:08am UTC](https://boards.straightdope.com/t/rifling-on-battle-tank-main-armament/549303/21 "2010-08-06T04:08:51Z")
> [@paperbackwriter](#): > > > [@Gray\_Ghost](#): > > > > For smoothbore MBT ammo, how do they get stability on non-saboted rounds, like HEAT or HEP? Or do HEP rounds used in smoothbores have fins too? Hard to kill dismounts with sabot rounds, though I suppose that’s what the coax is for… > > > > **Bear Nenno** , where are you…? > > HEP rounds are basically a British weapon. In the US Army they are only used on the M135 165 mm short-barrelled demolition gun carried on the [M728 Combat Engineer Vehicle](http://en.wikipedia.org/wiki/M728_Combat_Engineer_Vehicle). This is a rifled gun. > > The HEAT round for the M1 Abrams is [a fin-stabilized sub-caliber round that uses a sabot](http://www.defense-update.com/products/digits/120he-mp.htm), much like the APFSDS round. See the cutaway towards the bottom of that page. > > For dismounts, the Abrams uses the [canister round,](http://www.globalsecurity.org/military/systems/munitions/m1028.htm) essentially turning the tank into a 120mm shotgun, no need for stabilization. The HEAT round is full caliber, not a sabot round reference your link. The HEAT-MP round is a saboted sub-caliber round. - M1 Abrams rounds. The older rifled 105mm tank gun fired M393A1/A2 HEP rounds. Still stocked for Foreign Military Sales. This has been updated to the M393A3 for the mobile gun system Stryker vehicle. Recoilless rifles (definition varies - some call them rockets) like the Carl Gustav (84mm) and various other manufacturers (83mm and other calibers) have HEP/HESH warheads. Plasticized or squash warheads. There are also some breaching munitions and missile warheads with similiar characteristics. Spinning a HEAT warhead and resulting plasma jet with solid head (for a shaped charge with a liner) disrupts the jet and wastes energy available (angular momentum and all that physics stuff). You don’t need a liner to create a shape charge effect. Note that HEAT rounds do not “burn” through armor/concrete. It focuses extreme pressure against the target. The target material flows plastically away from the pressure point. Of course, this generates lots of heat leaving what looks like a “burn” but is an effect of the pressure/plastic flow. ---
**Author:** ![matt](https://avatars.discourse-cdn.com/v4/letter/m/a6a055/32.png) [@matt](https://boards.straightdope.com/u/matt)\ **Post date:** [August 6, 2010, 4:17am UTC](https://boards.straightdope.com/t/rifling-on-battle-tank-main-armament/549303/22 "2010-08-06T04:17:02Z")
> [@Really\_Not\_All\_That\_Bright](#): > > That’s just the point: even if you can only fire twice as many rounds before replacing an unrifled barrel, it’s still twice as many. If you’re saying that a rifled barrel wears out faster than a smoothbore barrel _in general_ then okay, all things (such as muzzle velocity) being equal. I understood your statement to mean that chemical energy munitions, i.e. explosive-filled shells, HEAT or HESH rounds, would wear out a rifled barrel faster than pure KE munitions, which didn’t make sense to me. ---
**Author:** ![crowmanyclouds](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crowmanyclouds/32/19884_2.png) [@crowmanyclouds](https://boards.straightdope.com/u/crowmanyclouds)\ **Post date:** [August 6, 2010, 7:00am UTC](https://boards.straightdope.com/t/rifling-on-battle-tank-main-armament/549303/23 "2010-08-06T07:00:53Z")
I used to know all this 20 years ago (learn a lot playing with pencil & paper RPGs\*) so, HESH High explosive anti-tank - non-penetrating, effect - chunks of spall shred things in the tank. HEAT High explosive anti-tank - sorta penetrating, effect - hot jet of molten metal (partly from the warhead, partly from the armor of the vehicle?) sprays things in the tank. APCR/APDS/APFSDS/FRAP/FAPDS/LRP/others? Kinetic energy penetrators - effect - high velocity metal rod punches through armor and bounces around hitting things in the tank, FRAP/FAPDS breaking into small pieces first. Am I remembering all this correctly? What’s the current ammo of choice for tanks with reactive armor, composite armor, and reactive over composite (assuming anyone’s combining the two)? CMC fnord! \*pencil & paper **R** ole **P** laying **G** ames - usefull pencil & paper **R** ocket **P** ropelled **G** renades - useless ---
**Author:** ![lazybratsche](https://avatars.discourse-cdn.com/v4/letter/l/ba8739/32.png) [@lazybratsche](https://boards.straightdope.com/u/lazybratsche)\ **Post date:** [August 6, 2010, 12:10pm UTC](https://boards.straightdope.com/t/rifling-on-battle-tank-main-armament/549303/24 "2010-08-06T12:10:45Z")
> [@matt](#): > > > [@Really\_Not\_All\_That\_Bright](#): > > > > That’s just the point: even if you can only fire twice as many rounds before replacing an unrifled barrel, it’s still twice as many. > > If you’re saying that a rifled barrel wears out faster than a smoothbore barrel _in general_ then okay, all things (such as muzzle velocity) being equal. I understood your statement to mean that chemical energy munitions, i.e. explosive-filled shells, HEAT or HESH rounds, would wear out a rifled barrel faster than pure KE munitions, which didn’t make sense to me. I think it’s simply that KE munitions have a very tiny moment of inertia (i.e. all the mass is concentrated in a dense “dart” right along the gun axis) so the rifling doesn’t impart much force to spin the munition. HEAT or HESH rounds are big and “fat”, and though I don’t know if they’re more massive, I’m certain they’ve got a larger moment of inertia since there’s more mass further from the barrel’s axis. The barrel rifling encounters much more force from those “fat” munitions, which makes it wear out faster. ---
**Author:** ![villa](https://avatars.discourse-cdn.com/v4/letter/v/bc79bd/32.png) [@villa](https://boards.straightdope.com/u/villa)\ **Post date:** [August 6, 2010, 2:35pm UTC](https://boards.straightdope.com/t/rifling-on-battle-tank-main-armament/549303/25 "2010-08-06T14:35:12Z")
I love this place. Not sure there’s anywhere else I could have got the same depth of response in the same time to a question that just popped into my head. Thanks everyone. ---
**Author:** ![msmith537](https://avatars.discourse-cdn.com/v4/letter/m/d9b06d/32.png) [@msmith537](https://boards.straightdope.com/u/msmith537)\ **Post date:** [August 6, 2010, 7:05pm UTC](https://boards.straightdope.com/t/rifling-on-battle-tank-main-armament/549303/26 "2010-08-06T19:05:47Z")
> [@paperbackwriter](#): > > For dismounts, the Abrams uses the [canister round,](http://www.globalsecurity.org/military/systems/munitions/m1028.htm) essentially turning the tank into a 120mm shotgun, no need for stabilization. Why would the Abrams need that? It already has a .50 caliber machinegun and two 7.62 mm machineguns for fighting infantry. ---
**Author:** ![crowmanyclouds](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crowmanyclouds/32/19884_2.png) [@crowmanyclouds](https://boards.straightdope.com/u/crowmanyclouds)\ **Post date:** [August 6, 2010, 7:22pm UTC](https://boards.straightdope.com/t/rifling-on-battle-tank-main-armament/549303/27 "2010-08-06T19:22:18Z")
> [@msmith537](#): > > Why would the Abrams need that? … Watch the last 15 seconds of [this](http://www.youtube.com/watch?v=Cgn1nhUEgo8). :eek: CMC fnord! ---
**Author:** ![Telperion](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telperion/32/509_2.png) [@Telperion](https://boards.straightdope.com/u/Telperion)\ **Post date:** [August 6, 2010, 7:23pm UTC](https://boards.straightdope.com/t/rifling-on-battle-tank-main-armament/549303/28 "2010-08-06T19:23:16Z")
> [@msmith537](#): > > Why would the Abrams need that? It already has a .50 caliber machinegun and two 7.62 mm machineguns for fighting infantry. It’s for when you absolutely, positively need to kill every motherf\*\*ker in the field. ---
**Author:** ![silenus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/silenus/32/166_2.png) [@silenus](https://boards.straightdope.com/u/silenus)\ **Post date:** [August 6, 2010, 7:35pm UTC](https://boards.straightdope.com/t/rifling-on-battle-tank-main-armament/549303/29 "2010-08-06T19:35:34Z")
> [@crowmanyclouds](#): > > What’s the current ammo of choice for tanks with reactive armor, composite armor, and reactive over composite (assuming anyone’s combining the two)? KEP. I don’t care how reactive your armor is, when it get hit with a depleted uranium dart at those speeds, the dart is out the other side before the armor knows it’s been hit. But IIRC we’ve never fought an enemy who used reactive armor, Or modern composite, for that matter. Most of the tanks we killed in Iraq weren’t front-line Western tanks. They were older, domestically-produced Russian models (T-72), among others (Chinese Type 69). ---
**Author:** ![notsoheavyd3](https://avatars.discourse-cdn.com/v4/letter/n/85e7bf/32.png) [@notsoheavyd3](https://boards.straightdope.com/u/notsoheavyd3)\ **Post date:** [August 6, 2010, 8:09pm UTC](https://boards.straightdope.com/t/rifling-on-battle-tank-main-armament/549303/30 "2010-08-06T20:09:57Z")
> [@crowmanyclouds](#): > > > [@msmith537](#): > > > > Why would the Abrams need that? … > > Watch the last 15 seconds of [this](http://www.youtube.com/watch?v=Cgn1nhUEgo8). :eek: > > CMC fnord! Cool, hey did you notice at around 30 seconds you can see it’s going super-sonic because you can actually see the shock wave coming off of it? ---
**Author:** ![Paul\_in\_Qatar](https://avatars.discourse-cdn.com/v4/letter/p/ccd318/32.png) [@Paul\_in\_Qatar](https://boards.straightdope.com/u/Paul_in_Qatar)\ **Post date:** [August 6, 2010, 8:19pm UTC](https://boards.straightdope.com/t/rifling-on-battle-tank-main-armament/549303/31 "2010-08-06T20:19:50Z")
[quote=“Mr.Excellent, post:15, topic:549303”] > [@paperbackwriter](#): > > Wow. That’s … cold. Do Abrams loaders customarily ask the tank commander if he’d care to give the enemy a whiff of the grape? Canister in the Tank World is called ‘Beehive.’ Unlike the old canister round, the modern type has a fuse that opens the shell at some preset distance from the muzzle. (The closest setting is called ‘muzzle action.’) It them releases a swarm of little needles called ‘fleshettes.’ They are quite nasty. Other rounds available for most guns are HC smoke, WP smoke and sometimes even illumination, although there is no need for that nowadays. As stated, a KE round can be fired out of a smooth cannon. This is the sabot round. There are also CE rounds that can handle a rifled gun, these are HEAPDS rounds once used by the Soviets. The are of course complex in their construction. ---
**Author:** ![crowmanyclouds](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crowmanyclouds/32/19884_2.png) [@crowmanyclouds](https://boards.straightdope.com/u/crowmanyclouds)\ **Post date:** [August 6, 2010, 8:36pm UTC](https://boards.straightdope.com/t/rifling-on-battle-tank-main-armament/549303/32 "2010-08-06T20:36:22Z")
> [@notsoheavyd3](#): > > Cool, hey did you notice at around 30 seconds you can see it’s going super-sonic because you can actually see the shock wave coming off of it? Approximately 1,150 10mm tungsten balls traveling at 1,400 m/s (3,132 MPH), ~Mach 4! That will ruin your [del]underwear[/del] day in ways a Ma Deuce just can’t. CMC fnord! ---
**Author:** ![RogueRacer](https://avatars.discourse-cdn.com/v4/letter/r/7ab992/32.png) [@RogueRacer](https://boards.straightdope.com/u/RogueRacer)\ **Post date:** [August 6, 2010, 8:37pm UTC](https://boards.straightdope.com/t/rifling-on-battle-tank-main-armament/549303/33 "2010-08-06T20:37:26Z")
> [@Paul\_in\_Qatar](#): > > It them releases a swarm of little needles called ‘fleshettes.’ Something looks odd about that. Not to nitpick, but I think that’s spelled “flechette”. ---
**Author:** ![Irishman](https://avatars.discourse-cdn.com/v4/letter/i/b487fb/32.png) [@Irishman](https://boards.straightdope.com/u/Irishman)\ **Post date:** [August 6, 2010, 8:42pm UTC](https://boards.straightdope.com/t/rifling-on-battle-tank-main-armament/549303/34 "2010-08-06T20:42:58Z")
**msmith537** said: > [@](#): > > Why would the Abrams need that? It already has a .50 caliber machinegun and two 7.62 mm machineguns for fighting infantry. The link you quoted by **paperbackwriter** said: > [@](#): > > This round meets urgent CINC, USFK requirements to provide effective rapid lethal reaction against massed assaulting infantry armed with hand held anti-tank and automatic weapons at close range (500 meters or less) thereby improving survivability. Additionally, this round will significantly increase the tank’s lethality and enhance the tank crew’s survivability. This additional capability will give the Abrams Tank the ability to survive RPG ambushes and to fully support friendly infantry assaults. In other words, you find your tank surrounded by a large group of RPG-wielding foot soldiers. Machine guns throw a lot of lead, but if the targets are scattered, it’s harder to hit them all. Machine guns work better on enfilading fire (i.e. down the line of targets) than across a line of targets. It also works better on emus. > **[Did the Australian army once wage war on emus?](https://www.straightdope.com/21344046/did-the-australian-army-once-wage-war-on-emus)** > [@](#): > > Resources assigned to the expedition consisted of two Lewis machine guns, 10,000 bullets, and a pair of gunners under the command of Major G.P.W. Meredith. A Fox Movietone cinematographer was sent along to film the highlights. Arriving in the town of Campion on November 2, 1932, Meredith’s troops drew first blood in a skirmish later that day, then established base camp on a local farm. The emus tended to stay near tree cover, making them unexpectedly difficult to shoot. On November 4 an ambush of 1,000 emus went awry when the machine gun jammed after only a dozen kills. An attempt to chase them with a truck-mounted gun likewise failed, as the gunner was too busy hanging on for dear life to squeeze off a single shot. > > By November 8 the army had reportedly used 2,500 rounds of ammunition to kill just 200 emus, leading the prime minister to suspend the campaign while anti-emu forces regrouped. [snip] > > A renewed assault beginning on November 13 wasn’t noticeably more effective, with a meager kill rate of 100 emus a week. The enemy proved to be fast, smart, and (Meredith insisted) capable of surviving multiple bullet wounds. > > By early December emu incursions had subsided, due more to the wheat harvest than casualties. Hostilities ceased on December 10. The official final tally: 9,860 bullets to kill 986 emus, an implausible ratio of exactly ten bullets per emu. ---
**Author:** ![paperbackwriter](https://avatars.discourse-cdn.com/v4/letter/p/53a042/32.png) [@paperbackwriter](https://boards.straightdope.com/u/paperbackwriter)\ **Post date:** [August 6, 2010, 9:07pm UTC](https://boards.straightdope.com/t/rifling-on-battle-tank-main-armament/549303/35 "2010-08-06T21:07:56Z")
> [@Paul\_in\_Qatar](#): > > Canister in the Tank World is called ‘Beehive.’ Unlike the old canister round, the modern type has a fuse that opens the shell at some preset distance from the muzzle. (The closest setting is called ‘muzzle action.’) It them releases a swarm of little needles called ‘fleshettes.’ They are quite nasty. True of the main gun on the old M60 but not of the Abrams. Take a look again at the cutaway posted above or the video **crowsmanyclouds** posted. Those are just balls of tungsten flying at you at very high speeds. ---
**Author:** ![Paul\_in\_Qatar](https://avatars.discourse-cdn.com/v4/letter/p/ccd318/32.png) [@Paul\_in\_Qatar](https://boards.straightdope.com/u/Paul_in_Qatar)\ **Post date:** [August 6, 2010, 10:05pm UTC](https://boards.straightdope.com/t/rifling-on-battle-tank-main-armament/549303/36 "2010-08-06T22:05:37Z")
> [@paperbackwriter](#): > > > [@Paul\_in\_Qatar](#): > > > > Canister in the Tank World is called ‘Beehive.’ Unlike the old canister round, the modern type has a fuse that opens the shell at some preset distance from the muzzle. (The closest setting is called ‘muzzle action.’) It them releases a swarm of little needles called ‘fleshettes.’ They are quite nasty. > > True of the main gun on the old M60 but not of the Abrams. Take a look again at the cutaway posted above or the video **crowsmanyclouds** posted. Those are just balls of tungsten flying at you at very high speeds. You forget I am about a million years old. Heck, I remember ranging machine guns (although I never used one). ---
**Author:** ![Patch](https://avatars.discourse-cdn.com/v4/letter/p/a183cd/32.png) [@Patch](https://boards.straightdope.com/u/Patch)\ **Post date:** [August 12, 2010, 2:08pm UTC](https://boards.straightdope.com/t/rifling-on-battle-tank-main-armament/549303/37 "2010-08-12T14:08:01Z")
> [@paperbackwriter](#): > > > [@Paul\_in\_Qatar](#): > > > > Canister in the Tank World is called ‘Beehive.’ Unlike the old canister round, the modern type has a fuse that opens the shell at some preset distance from the muzzle. (The closest setting is called ‘muzzle action.’) It them releases a swarm of little needles called ‘fleshettes.’ They are quite nasty. > > True of the main gun on the old M60 but not of the Abrams. Take a look again at the cutaway posted above or the video **crowsmanyclouds** posted. Those are just balls of tungsten flying at you at very high speeds. I wonder why they moved away from flechettes? I know a tanker from the Vietman war, and he loved the stuff ---
**Author:** ![Patch](https://avatars.discourse-cdn.com/v4/letter/p/a183cd/32.png) [@Patch](https://boards.straightdope.com/u/Patch)\ **Post date:** [August 12, 2010, 2:11pm UTC](https://boards.straightdope.com/t/rifling-on-battle-tank-main-armament/549303/38 "2010-08-12T14:11:50Z")
> [@silenus](#): > > > [@crowmanyclouds](#): > > > > What’s the current ammo of choice for tanks with reactive armor, composite armor, and reactive over composite (assuming anyone’s combining the two)? > > KEP. I don’t care how reactive your armor is, when it get hit with a depleted uranium dart at those speeds, the dart is out the other side before the armor knows it’s been hit. But IIRC we’ve never fought an enemy who used reactive armor, Or modern composite, for that matter. Most of the tanks we killed in Iraq weren’t front-line Western tanks. They were older, domestically-produced Russian models (T-72), among others (Chinese Type 69). I do believe the Russians have adapted reactive armor to work against KEP projectiles. [It’s called Kontakt-5](http://en.wikipedia.org/wiki/Kontakt-5). ---
**Author:** ![Sailboat](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sailboat/32/461_2.png) [@Sailboat](https://boards.straightdope.com/u/Sailboat)\ **Post date:** [August 12, 2010, 6:05pm UTC](https://boards.straightdope.com/t/rifling-on-battle-tank-main-armament/549303/39 "2010-08-12T18:05:46Z")
> [@matt](#): > > With tank guns there’s two ways to go: 1) the slightly more accurate rifled gun, which can shoot HESH and other HE rounds, but needs specialised shells to shoot non-spinning HEAT and KE penetrators, or 2) the less accurate smoothbore gun that shoots HEAT and HE penetrators with ease,but needs fin stabilisation or shells with tails to shoot e.g. HESH or smoke. Competing technologies, and the smoothbore seems to have won. Interestingly, I read that in the initial testing the US and UK conducted while trying to decide between these two, the exact opposite effect from what one would expect occurred. The 105mm _rifled_ gun, supposedly more accurate but not as hard-hitting, showed greater penetration and less accuracy. The 120mm _smoothbore_ gun, supposedly less accurate but harder-hitting, scored better accuracy with lower penetration. I read that several times, assuming I’d misread it, and that seems to be what they concluded. ---
**Author:** ![Really\_Not\_All\_That\_Bright](https://avatars.discourse-cdn.com/v4/letter/r/e8c25b/32.png) [@Really\_Not\_All\_That\_Bright](https://boards.straightdope.com/u/Really_Not_All_That_Bright)\ **Post date:** [August 12, 2010, 6:09pm UTC](https://boards.straightdope.com/t/rifling-on-battle-tank-main-armament/549303/40 "2010-08-12T18:09:12Z")
I do recall that the Challenger II’s current gun holds the record for the longest-range confirmed tank kill, during the first Gulf War. Presumably that wasn’t against reactive armor, though. [Previous page](https://boards.straightdope.com/t/rifling-on-battle-tank-main-armament/549303.md?page=1) [Next page](https://boards.straightdope.com/t/rifling-on-battle-tank-main-armament/549303.md?page=3)