Yes, 120mm soft launch brilliant rounds-
http://www.youtube.com/watch?v=oY9S-PcKLYs
Are superior to 120mm high velocity KEPs in the AT role for a number of reasons, mostly having to do with the weapon it is fired from:
1. AMOS (twin barrel, auto breachloading turret) can be put on almost any chassis, including the M113, CV-90 and several Wheeled types. Which means you can deploy it in less than 60 days.
http://www.youtube.com/watch?v=TBqqWknHVqc
2. Rate Of Fire is vastly superior, on the order of 24 shots per minute to the steady 6-8 and surge speed 10-12 that an Abrams can put out. Some MBT are better at ROF because they are autoloaded but even those rarely exceed 15spm.
3. The Mortar has superior range. On the order of 12-15km. This is well beyond LOS in most conditions and allows the unit to fire indirectly in modes which the threat tank _cannot_ respond to without going indirect itself. The latter options is not impossible, the M1 having gone through three iterations of XROD, STAFF, TERM and now MRM guided development programs, but the point is that it doesn't buy you anything because by the time the either round arrives both are defendable against with APS like the Arena and Trophy as well as advanced ERA like CACTUS.
4. Soft launch is a lot less hard on the missiletronics. Keeping in mind the 30,000G that the Copperhead endured.
5. Tanks suck in a lot of important areas like mountains and swamps and narrow streets. Iraq has seen a lot of Abrams end up spilled because they went down a soft dirt berm between two flood control areas and had the road collapse under their weight. They routinely beat up tiny streets to the point where massive repair budget is (or was) allocated for NATO Germany. And in AfG's 'hills' their typical 15-20` of barrel elevation vs. the 85` of the AMOS turret makes them useless against RCL and LAW as well as direct fire from the heights of surrounding ridges. Indeed, their top armor and sighting systems are also exceptionally poor to the extent that a command is often reduced to opening his hatch to bullets coming in to find targets for his .50, even assuming he has electric drive to remote it.
6. Gun shortcomings also applies to the way that ammunition is used. Current tests with modernized beehive rounds like the XM1028-
http://www.youtube.com/watch?v=Cgn1nhUEgo8
Show the lethal downrange risks of firing this kind of ammo. Similar problems exist with mixed sabot and heat rounds in that you will perforate several houses and collapse entire buildings respectively when firing at guerillas with the main tube. Sometimes this is useful as it certainly teaches a lesson about lingering too long to ambush and snipe from behind our infantry. More often than not, it is fly hunting with a sledgehammer.
OTOH, a 120mm mortar can theoretically do the same thing if it has a HESH or HEP head with a big enough bang in it. But it can also be fire from a centralized location (i.e. never leaving the FOB) and still plunge vertically to hit just one intersection. Covering multiple patrols.
7. The 120mm usually has more and more diverse ammo. Smoke, Illumination, AT, Frag, HE. With various airburst and penetration fuzing options as well. A typical NLS loadout (BAe's single barrel AMOS) is around 70-80 conventional rounds with another ten 'specials' in a side compartment. This is compared to the 40-42 you can stuff in an Abrams.
http://www.globalsecurity.org/military/systems/ground/m1-specs.htm
http://www.thefreelibrary.com/Fast+moving+120mm+mortars:+the+120-mm+mortar+is+the+largest+indirect+...-a0171018005
Of course there are conditional modifiers here. You don't really want the US Army solution of a 120mm breach loader in the back of a Stryker. First, because the 120mm is so heavy they actually have a secondary 89mm (and ammo and training costs) to go mobile with. Secondly because the days of open hull AFV should have ended with the gun carriers and halftracks of WWII. If you tie into it with another artillery shooter, high angle threats (buildings and mountains again) or start to face top attack systems of any kind (an RPG against an adjoining wall, a rifle grenade from 400m, a handgrenade from 30, or an RBS-56/AT-14 Kornet from 1,500) you really don't want to be open airing it from even a near miss. Under Armor is the way to go because it allows for faster onset of fires across 360` and more systems integration to properly place them while keeping the crew free from small arms risk if the weapon must be used essentially as an assault gun. Which the TMS/AMOS can also achieve, out to about 1,200m or so.
CONCLUSION:
The fact of the matter is that tanks are dinosaurs. They really should have been pulled from the front lines years ago but because they represent a technological 'epoch' they have a use in keeping the competition restrained to a specific class limitation of performance to which basic improvements in the three primes of protection, mobility and firepower render the system easy to upgrade. There is also a considerable institutional inertia, at least in the U.S. Army center around heavy-tread systems. What Shinseki I think it was did when he wanted to go to the wheeled 'light brigades' is threaten to make public an image of a LOSAT which, fired 8 at a time from a Hummer, went in the front grate and out the back engine grill of an M1A2. This is the reality of LOS warfare, in that, if you can sustain the speed of the round at the muzzle (via rocket propulsion), there is not a tank on the planet which can withstand any of the modern 120-125mm rounds. And using the concept of a Modern ONTOS (LOSAT has been killed by politics by CKEM can go on systems as small as a robotic MULE) you can guide eight shots before the first enemy round hits you.
And this is the critical reality we are talking about here.
Because it's not the first minute that counts. It's the first 10-15 seconds which decides tank combat at anything under about 2,500-3,000m these days. Everyone (including the Russians) have modern fire control and decent rounds. Such that anybody shooting that gets a hit is likely to get at least a mission kill as the turret jams or the vehicle stops moving.
If a missile carrier can fire 8 rounds in 10 seconds it beats 8 tanks with manual loading or 4 tanks with autoloaders and it does so at distances beyond that which their own kinetic energy penetrators can guarantee a hit.
If you cannot beat the rapid fire, cheap, solution at LOS distances. And you cannot bring enough tanks to beat an enemy equipped with T-90 or Leo-2A6 to a distant theater quickly enough, then you had better go for an alternative 'netcentric' approach which puts the shooter into NLOS and saturates any Automatic Protection Systems with MRSI simulshots. We could do exactly this, begin killing enemy tanks in maneuver warfare SOONER and FASTER that could be achieved with direct fire systems. But we would first have to show that these thin skin, easily deployed, easily hidden, bushwackers can also survive 4th generation warfare against whomever we label insurgents, fighting with RPG at <200m distances.
The irony then becomes that in a role for which they are not optimized, tanks remain able to soak a lot of desultory fires with minimal damage gen-after-next 'light' systems are better at open field maneuver warfare.
If we could bring small scale Wiesel type robotic vehicles into MOUT service with light cannon and ATGW atop minimally armored hulls in the 5-10 ton class, we could ditch tanks altogether and save HUGE amounts of money in yearly maintenance and training alone. But so long as it's high-tech vs. old-iron in street fighting, the tankers will snicker and keep their rides because, nominally, they are 'cheaper' to shoot up.
