I see very interesting for tanks to have ammunition that allows them to fight outside the range of the portable/man-portable weapons, which limit is marked by 120mm light mortars with rocket assisted ammunition.
Why? Because it would allow to the tanks to attack infantry formations without support of heavy weapons from outside the range of every weapon that they have, without risk, and would reinforce very significantly the action of the artillery and the Surface-Surface weapons (both habitually present in much lower amounts).
Dude... when a tank is facing portable anti tank weapons it wont be firing DU rounds... it will be firing HE rounds... a T-72 can fire HE shells to about 9km based on elevation limitations of the main gun... park on a hill and you could probably fire rounds three or four times further.
While I tend to think that the 152mm caliber is very interesting for the tanks in the armata platform and will succeed, I expect also rocket assisted ammunition for the 125mm caliber and the current tanks. 125mm ammunition always should have bigger range than the 120mm ammunition of the same type (also of other countries), and this would mean a range of around 17-18 Km.
In theory a 125mm gun should be more powerful than a 120mm gun, but then the difference wont actually have that much practical difference.
It is like 7.62 x 54mm ammo compared with 7.62 x 51mm. When loading for hunting you can load heavier bullets in the Soviet round because its case is bigger but in terms of effect on target I very much doubt the target would actually notice the difference in bullet weight or speed.
In overall terms a rocket assisted system would be compatible with every type of ammunition. Here little problem.
Also, on land, the maximum limit of the portable/man-portable weapons is done by light mortars, portable 120mm mortars, that have also rocket assisted projectiles and guided ammunition that can be used vs tanks, from outside of the range of the tanks, and the tank would not be able to answer except if the tank is provided with 125mm rocket assisted ammunition.
In the game of ranges the tanks must be winner at every range over infantry weapons. No excuses.
120mm mortar is not "portable". They require to be towed by motor vehicle. 60 and 81/2mm mortars are carried by infantry, 120mm no.
Tanks lack awareness for the most part to be able to explot advantages of long range munitions, even with support of UAVs and various BMS platforms it will keep being so for long time.
These days there are ATGMs that are reaching ranges of 10km, even more, however 95% of the time in combat its out of the question that ATGM team will be able to exploit all of its range. Battlefield is almost never, if ever plain field.
Yes they are carried by infantry.
Even the 2B23 120mm mortar was designed to be man-portable, divided in 4 or 5 parts. It is man-portable.
But also other 120mm mortars are "portable" in the sense that can be transported inside vehicles without limitations or need of special designs (even in a civil car), in the same way that other infantry weapon or ammunition. "Portable" mortars, like the 2B11 and the PM-38, require not a tractor element like the heavy artillery, despite can have them in some cases.
They are weapons of small relative size and weight. Today the portable/man-portable weapons of Russia would be the weapons under 500 Kg, taking into account that between 300 and 500 Kg Russia only has the 2B23 (man-portable in parts).
Finally, the commented for formations of multiple units and its deployment is valid for both sides. Both sides want to leave not hidden places for the adversary. The terrain is not plain but a good positioning of the own units try to avoid to leavy positions where the adversary can be covered by the terrain.
120mm M75 mortar we use here is 262Kg with its transport mount, that is not, by any means portable. Portable is when you can divide our M57 mortar and two-three men and carry it for 20 miles into mountain.
Our M-74 was lighter version which was desiegned to be carried by horses or donkeys for mountain units, again, not men. However it was very rare i doubt any remain in service up to this time, lower weight had in return far lower rate of fire and general lifespan.
M-75 is attached to TAM-110 for towing, or some other motor vehicle in that class, by standard it was TAM-110, again i never saw it being handled by hands for more than 100-200m tops, where someone prepared firing position. 81/82mm mortars yes.
Let alone fact that 120mm mortar detachment consists of 2 com officers, scout, sighter, ballistics calculator, then for each of 4 mortars there is aimer, two shell handlers and fuser.
Your comment looks pretty archaic, even using miles still
About to carry the mortars, what do you mean? to carry them like in the XIX-century? walking, with horses or donkeys? or to carry them in a modern way, in their vehicles... Today even the airborne troops have their own vehicles...
A light 120mm mortar, like those between 200 and 300 Kg are easily portable in every infantry vehicle, without adaptations, without a need of towing. They are not exactly man-portable, but I know people that can up them to inside a vehicle alone, without help. The light mortars of 120mm give not problem to be carried today, this is why I use the "portable/man-portable" formulation to talk about the weapons that need nothing aditional or specific to be transported by the infantry. There is not doubt that today these light 120mm mortars are infantry weapons.
Other question is a mortar like the 2B9 Vasilek, with over 600 Kg, and more difficult dimensions to be transported. This is just the main reason of its decline.
Surely the design of the PM-38/43 light mortar of 120mm has been one of the most outstanding designs of the WWII, remaining almost without changes until now. The PM-38 is a 79 years old weapon, and its design remains very actual and useful today. To transport a mortar like this today is nothing for an armata platform vehicle (very interesting fire power complement for the T-15 or even for this BMP-T Terminator-3). In fact, can be done by every infantry vehicle and civil car.