How do these two tanks compare? AFAIK the Challenger II is newer, is it better?
No idea as to comparisons, but the BBC has a couple nifty “facts” pages.
Challenger II.
http://news.bbc.co.uk/1/hi/uk/2519005.stm
Abrams.
http://news.bbc.co.uk/1/hi/world/americas/2516691.stm
And as long as I’m here and the Beeb is being so obliging, the Iraqi Lion of Babylon, which gets my vote as “Coolest Tank Name”. 
http://news.bbc.co.uk/1/hi/world/middle_east/2843367.stm
Well “better” is more of an IMHO than a GQ, but here’s some factual data.
Challenger 2
Crew: 4
Armament: 120mm gun, 7.62mm coaxial MG, 1 7.62mm AA MG, 10 smoke dischargers.
Ammo: 52 120mm rounds, 4,000 7.62mm rounds
Length (over gun): 11.55 m.
Hull length: 8.327 m.
Width 3.52 m.
Height: 2.49 m.
Ground clearance: 0.5 m.
Combat weight: 62,500 kg.
Power-to-weight ratio: 19.2hp/tonne
Ground pressure: 0.9 kg per square cm.
Engine: Perkins Engines Condor V-12 diesel, 1,200 bhp at 2300 rpm.
Max road speed: 56 km/hr
Range: 400 km.
Fuel capacity: 1797 liters
Fording: 1.07 m.
Gradient: 60%
Side slope: 30%
Vertical obstacle: 0.9 m
Trench: 2.34 m.
Armor thickness: ???
Armor type: Chobham/steel
NBC system: Yes.
Night vision: Passive, for commander, gunner and driver.
M1A2 Abrams
Crew: 4
Armament: 120mm gun, 7.62mm coaxial MG, 7.62mm AA MG, 1 12.7mm AA MG, 12 smoke dischargers.
Ammo: ? (original M1 had 55 105mm rounds, dunno how many 120mm the new one has). 1,000 12.7mm rounds, 11,400 7.62mm rounds.
Length (over gun): 9.8 m.
Hull length: 7.9 m.
Width: 3.65 m.
Height: 2.38 m.
Ground clearance: 0.482 m
Combat weight: 54,545 kg
Power-to-weight ratio: 27 hp/tonne.
Engine: Textron Lycoming AGT 1500 turbine, 1500 hp at 3,000 rpm.
Max road speed: 72.4 km/hr.
Range: 498 km.
Fuel capacity: 1,907 liters.
Fording: 1.219 m.
Vertical obstacle: 1.244 m.
Trench: 2.743 m.
Gradient: 60%
Side slope: 40%
Armor thickness: ???
Armor type: Laminate/steel
NBC system: Yes.
Night vision: Passive, for commander, gunner, and driver.
For my money, if I were in Iraq right now, I’d rather be in the Abrams. Better speed and horsepower=weight ratio when it’s time to get the hell out of Dodge, lower frontal profile, more smoke to hide behind, more machine gun ammo. It’s hard to be sure without knowing the armor thickness, though. That extra 7,000 kilograms the Challenger is carrying might represent a lot more protection, or it might just represent bad design. I don’t know.
I’d rather be in a Merkava than any of them. So nice to have a big, thick engine between me and the enemy.
Thanks, they sound pretty similar to me. Maybe the M1 has the edge, I guess it all depends upon how good that secret Chobam armour really is.
This bit about the Iraqi tank from DDG’s link:
is either a.) in error, or b.) explains why they seem to like to use them in dug-in positions.
Talk about bad gas mileage!
Lemme guess, 1,800 meters is the maximum range the Iraqis can PUSH the the tank (to make it go) before they get too tired 
Ringo -
I believe that 1800 meters is the effective range of the main gun, not the distance that the vehicle can travel on a full load of fuel 
IIRC the longest tank-tank “kill” in Desert Storm was a British Challenger destroying an Iraqi tank at a distance of about 5km. I’ll dig up the cite if anyone wants it.
The Challenger 2 has second generation Chobham Armour, making it the best protected tank in the world, which I think may be a plus point over the Abrams (unless that has been upgraded to 2nd gen as well).
IIRC, Chobham armour has a distinct advantage for protection against HEAT anti-tank weapons,or anything that uses a hot core.
What?
Are you afraid the USicans and the UKians might get into a disagreement over the spoils of war? 
Peace,
mangeorge
Well, the 120mm gun on the Abrams is smoothbore, firing finned projetiles, while the Challenger II has a rifled barrel. In tank-to-tank fights, the smoothbore allows for higher velocity projectiles, and is more effective when fireing armor piercing rounds and HEAT rounds; the rifled barrel is better for HE rounds, which are typically not used on tanks, but other targets. Also, accourding to this site, http://www.pbs.org/wgbh/pages/frontline/gulf/weapons/m1.html the armor on the Abrams is a ceramic/steel plate that is very similar to the Chobham you see on the Challenger II.
I read somewhere that the exact specs of the Chobham armour is classified, so it’s difficult to predict exactly much protection is offers.
No, but when you consider the current rate of friendly fire accidents, it may only be a matter of time before we see which is best at knocking out the other. 
As for Chobham armour, I have a 20 year old magazine article here explaining in simple terms (perhaps obvious even) what its effect is on different rounds. The diagrams show the Chobham armour as an outer skin, on top of the tanks hull.
APDS: Laminated armour resists penetration to a much greater extent, so the sabot is less likely to reach the hull of the vehicle.
HEAP: The explosion is directed outwards by its failure to penetrate the armour (although you still get a mighty shockwave according to the picture here).
HESH: The shockwaves are re-directed along the armour and dissipated in the laminate construction.
HEAT: The laminated armour conducts heat away from the site of detonation. (the accompanying diagram shows limited damage to the tank hull, but there is some)
I think the Challenger II is designed to be better protected from missiles hitting from above(where the armor is thinnest on most tanks). That might explain some or all of the weight.
Heh. Rusty gearbox, and that’s not the T-72 I’m referring to.
There’s a huge thread at Fark on this from yesterday,click here