Challenger v Abrams: Who Wins?

In the Top Gear episode I was watching last night, Jeremy Clarkson was testing the Range Rover Sport. In a typical Top Gear challenge, he took it off road while being pursued by a Challenger II tank. (Clip below)

During the set-up, Clarkson noted:

"The thing I'm interesting most interested in, though, is the big gun, which, as you can see is rifled for greater accuracy. Unlike those smoothbore American ones, which just hit something [pauses and waves off at the distance,dismissively] over there."

Which got me to wondering. Suppose you matched up equal forces of US Abrams M1A2 tanks and UK Challenger IIs. No supporting artillery or infantry. No air support. Just tank on tank, with the best troops of both nations. All else equal, who would win?

BTW, Wikipedia reports:

The Challenger Lethality Improvement Programme is a programme to replace the current L30A1 rifled gun with the 120 mm Rheinmetall L55 smoothbore gun currently used in the Leopard 2A6. The use of a smoothbore weapon allows Challenger 2 to use NATO standard ammunition developed in Germany and the US. This includes more lethal tungsten-based kinetic energy penetrators, which do not have the same political and environmental objections as depleted uranium rounds. The production lines for rifled 120 mm ammunition in the UK have been closed for some years, existing stocks of ammunition for the L30A1 are finite.

A single Challenger 2 was fitted with the L55 and underwent trials in January 2006.[14] The smoothbore gun is the same length as the L30A1, and is fitted with the rifled gun's cradle, thermal sleeve, bore evacuator and muzzle reference system. Early trials apparently revealed that the German tungsten DM53 round was more effective than the depleted uranium CHARM 3.

So the smoothbore gun's ammo is "more lethal" and "more effective." So much for the vaunted superiority of British rifled gun tubes, eh?

Update: To answer a reader question, I'm not unaware of the prodigious Leopard 2A6. A formidable main battle tank, it is (to quote Yoda). But it's not in the video, now is it?

Comments

[C.E. Petit]

This is a typical amateur's comment: A smoothbore musket is less accurate than a rifled musket, therefore a (vastly larger) smoothbore cannon must be less accurate than a rifled cannon. One problem: Smoothbore muskets fire(d) roughly spherical balls; smoothbore cannon fire ogive-nosed spin-stabilized cylinders.

I've been itching to find a way to call Clarkson an "amateur" for quite a while {vbeg}

[Flighterdoc]

Yeah, the Abrams fires and hits "something" "over there".

In Desert Storm, "something" was two T-70 Soviet Tanks (one was in back of the other, and unseen by the tank crew) and "over there" was more than 4 km away.

Oh, and that was with the less capable DU round. The US Army has Tungsten penetrators too.

[Mike Puckett]

Wiki Bullshit. DU rounds self-sharpen. Tungsten blunts. DU is a superior armor piercing material. And it's Pyrophoritic to boot.

[canuck49]

Jeremy Clarkson is a rude, chauvinistic jackass with a juvenile, attitude and a big mouth.

[James]

Yeah, that "inaccurate" 120mm smoothbore that can get off about double the shots as that Challenger's main gun.

[ddd]

Sabot rounds (solid tungsten or depleted uranium bolts) are too long to be spun at high enough speeds by barrel rifling. With the invention of fin stabilized discarding sabot rounds (darts, basically) it was found that spinning actually decreased accuracy - the fins do the job of flattening trajectory and providing in flight stability that rifling would normally do. Thus the move to smoothbore barrels for guns that are primarily required to penetrate heavy armor. The only guns with this requirement are on tanks these days, as missile technology has rendered armor belts on warships obsolete and counterproductive. So yes, the abrams has an advantage as far as main gun is concerned.

An interesting question is what effect smoothbore has on accuracy of high explosive anti tank rounds, which are more traditionally bullet shaped and hollowed to carry explosives, but not the first choice for anti-tank duty despite their name. Unless the shell itself somehow provides the spinning motion those rounds should indeed be much less accurate.

[DaveP.]

Um, Jeremy? English guns are rifled because when the Challenger was designed the English armored froces still thought that HESH was the be-all, end-all of antitank shells. The Americans (and the Germans, and the Israelis, and the Russians, and the Chinese) expect to kill a lot of targets with APFSDS, so they use smoothbore.

IOW: England (which hasn't had to fight a tank-on-tank battle since 1945) is only now starting to switch form an outmoded concept that never worked as designed in the first place... to what everyone else in the known world was using in the first place.

Wanker.

[MB Kitchen]

For Sale: Lightly used 1998 BAE Challenger 2, two tone sand and fern paint job, rifled barrel, 1000+ HP Diesel, IR, Therm, NV, low mileage, very well maintained, NUIB (never used in battle). Call: BR549 ask for Gordon, Bob, or Quentin.

[J.M. Heinrichs]

You might check here for some supporting info: http://en.wikipedia.org/wiki/Canadian_Army_Trophy

Cheers

[Stephen Green]

Challenger v Abrams? In all honesty, the result would depend entirely on the training & experience of the crews.

[Steven Den Beste]

When a tank is trying to destroy enemy armor, since the 1960's there are three main kinds of shells that can be used.

The first kind is called HEAT, High Explosive AntiTank, and it is a shaped charge. The front of the charge is an inverted cone plated with (usually) copper. There's a fuse sticking out in front, a long narrow stick.

The explosion starts in the back and burns forward, and eventually what it does is to melt the copper and compress it into a narrow stream which travels forward at very high speed and pressure. Ideally it cuts through the armor and destroys what's on the other side.

The second kind is called HESH (High explosive shaped charge) or HEP (High Explosive Plastic). It's a pretty thin shell full of plastic explosive, and it has a delayed fuse. When it strikes its target it doesn't go off immediately. Instead, the case ruptures and the plastic explosive forms a mound on the armor, and THEN it goes off.

This puts a divot into the metal, but that doesn't penetrate all the way. It also causes an extremely powerful shock wave, sound, which travels through the armor to the inside where it knocks loose some of the armor itself, a process called "spalling". It is pieces of the enemy tank's own armor that then kills its crew and causes other damage.

Those are both explosive. The third kind is not. It's called APFSDS, Armor Piercing Fin Stabilized Discarding Sabot, and it's usually referred to as "sabot" (which is pronounced say-boh). It's a metal dart, sharp in the front and with fins in the back. It is much more narrow than the gun barrel it's fired out of, so to seal the gun barrel during the firing process there are two or three sabots which fill the rest of the space and seal it. Once the round is out of the gun, the sabots separate and fall away, and the penetrator (the dart) proceeds to the target. The penetrator strikes the enemy armor and if it's moving sufficiently fast it will go right through it and destroy whatever is on the other side.

The penetrator can be made out of anything heavy and dense and hard, but uranium is best. If it's made of something like tungsten, the impact will blunt the tip and it won't penetrate as well. Uranium is self-sharpening; some of the metal burns off as it's moving through the armor, and the front remains sharp all the way.

Which brings us to the question of smooth bore and rifled guns. The key here is that HESH requires a rifled gun, but sabot and HEAT don't like them.

Because the shell of a HESH round isn't very strong, the round can and probably will deform during firing. That throws off its aerodynamics and makes it inaccurate. A rifled gun solves that because a shell which is lopsided but spinning rapidly acts like it isn't lopsided.

But a rifled gun is a problem with HEAT and sabot rounds. If a sabot round is spinning too rapidly when it emerges from the gun, the sabots have a difficult time separating cleanly. As to HEAT, if the round is spinning too rapidly, it interferes with formation of the jet of molten copper upon impact.

The US used a rifled gun in the M-60, which could fire all three kinds of rounds. The way they used HEAT and sabot was that the rounds were covered with a sheath of plastic. When the round was fired out of a rifled gun, the plastic would erode off as the shell went out, and it wouldn't pick up much spin.

But with the M1, the US switched to using that German smooth-barrel. That means that the M1 can't fire HESH.

But there's no good reason to do so anymore. HESH turns out to be virtually useless against "Chobham" laminated armor, which has been standard for NATO tanks since the 1970's and is also pretty much standard for late Soviet era tanks. When American tanks fire at Russian tanks (for instance, in 2003 in Iraq) they fire sabot, which works just as well against laminated armor as against solid armor.

As to accuracy? You don't need rifling for accuracy. What you need is consistency in your ammunition (i.e. good production quality) and excellent firing electronics, and the M1's got it.

Now as to the British rifled guns, the reason they stayed with that was because the British like using HESH. It's an institutional thing. But as laminated armor becomes more and more common, it's reached the point where it's even obvious to the Brits that HESH is a waste of time, and there's no other reason to stay with a rifled gun. They're actually worse than smooth bore for firing HEAT and sabot.

[www.facebook.com/profile.php?id=660690261]

One of the reasons we use the smooth bore gun is the sabot round. The sabot will fire with a rifled barrel but it actually causes the penetrator to lose some of its kinetic energy which is imparted to spin the round. Sorry Brits our gun is better.

[dick]

I'd be more than happy to pit American Treadheads in an M1 against any tank manufactured, by any country, and operated by any army.

[Jon]

The M1 fires fin stabilized ammunition, which is more accurate than the ammunition fired by the Challenger.

[robotech master]

Just to note many ppl believed that Challenger was crap and was going to be worthless in iraq. It was the lowest scoring tank in many of the tank games... Now its proven to be as good tank as any other abrams clone but its really a matter of the battle field its in. The US abrams has alot of high tech targeting, comms other gear that give it the edge over its brit counter part.

I think most tank runners are going to wage on the abrams depending on the model...

[dlowie]

I'm an amateur also so cannot verify the accuracy of this. U238 is supposedly more effective than tungsten for 2 reasons. 1st it shears off as it strikes leaving a sharp end that allows greater penetration (tungsten mushrooms and crumbles) and 2nd it's ability to be thermally labile allowing much greater internal destruction to enemy vehicles. Finally my own thought on the advantage of smooth bore over rifled bore is that the shell doesn't have to engage the rifling and so can carry more energy straight forward rather than in angular momentum. The only way to ameliorate this disadvantage is a gain twist in the rifling.

[Dave]

A projectile needs to be stabilized to be accurate. You can spin the projectile with rifling or use a stabilizer like fins. Thirty years ago, they found out that the tank rounds had less penetrating power at long distances with the rifled barrel. The original M1 Abrams had a rifled barrel and switched to a smooth bore back in the 1980's. I'm actually surprised to find out that the Challenger was still using a rifled barrel.

[Eclecticmeanderings.blogspot.com]

Greate video.

The Abrams, Challenger, Leopard, and T90 are roughly of the same generation. Being in the sights of any of them is not recommended. They are all good enough that it is most likely crew training and team work that would decide the issue.

The advantage of a smooth bored gun is that it fires kinetic energy (fin stabilized) rounds more accurately and forcefully than rifled guns. Kinetic energy rounds are more effective than High Explosive rounds in fighting other tanks. This was known to the gunnery geeks before the 1973 war and became very apparent after the war when the damage caused by Soviet smooth bore guns was compared to NATO rifled guns.

*Kinetic energy rounds work when a piece of high grade steel or depleated Urainum traveling at Mach 6 or better hits the enemy tank forcing a hole.

[JorgXMcKie]

I'm still looking for a copy of a video that I saw back in the 90s that showed, I believe, a US Abrams M1 tank company sweep through an Iraqi tank brigade during Gulf War I. They were moving at speed [50MPH?} and firing as they went. I understand some of them exceeded what was believed to be the top firing rate.

Anyway, it went: point, fire, hit, move to next target. They went through once then swept back to hit anything not destroyed on the first path. There was little but burning hulks of Soviet tanks, trucks, etc.

Perhaps it could be found and shown to Clarkson as an example of the Abrams' accuracy.

[Joe Hooker]

Not so, C.E.

Modern tanks w/ smoothbore guns e.g. M1A1 fire a fin stabilized sabot projectile that does not spin. It looks like a steel arrow. They are quite accurate and will match or beat a rifled tank gun any day.

[John Lynch]

It would come down to crew skill. British tankers are very good. So are ours. Tank battles are more about who maneuvers better, not just guns and armor. Side and rear shots are what it's about.

If you want to game it out, try Combat Mission: Shock Force. It's available at battlefront.com.

[gaston]

I don't know of a tanker on the planet that except for Nationalistic pride would want to fight in anything except for the M1A2 Abrams SEP tank. Proven in more combat than any other tank. More tank kills than any other tank. Faster and more agile. I believe the Leopard and the Abrams M1A2 use the same gun, just that the Abrams has a higher technology gun sight.

Sure there are other good tanks out there, but none of them have excelled in as much real world combat as the Abrams.

[C.E. Petit]

Silly me, typing too fast: fin-stabilized cylinders.

[Keith]

Part of the accuracy of the smooth-bore fired "sabot" round is in the fact that, after fired, the shell peals off leaving fins to produce the spiraling effect normally generated from the rifling.

The superiority of accuracy and effect-on-target of the smooth-bore barrel comes from the fact that--without the resistance generated from rifling in the barrel--the round is allowed to excelerate more quickly thus achieving remarkably high speeds. These high speeds allow it more accuracy (less time in air means adverse factors have less time to affect the round's trajectory) and far more kinetic lethality. So much so that armour penetrating sabot rounds do not require an explosive warhead. The mere impact literally detonates the target's armour and the sabot bolt penetrates straight through.

Just so ya know.

[Steven Den Beste]

I blew it. HESH is High Explosive Squash Head.