shiv, This is called hypersonic lift. Its proportional to the Mach number and the L/D ratio of the body.
L/Dmax = 4(M+3)/M a value purely driven by Mach Number.https://en.wikipedia.org/wiki/Lift-to-drag_ratio
In high mountains the hypersonic lift contributes to overshoot. So the trajectory has to be more high angle to make the shell fall. Or fire with reduced charge to reduce the Mach number.
Germans found this out in high altitude warfare in the Alps.
Shells tend to overshoot.
I guess the same effect with rockets too, the air being lighter resulting in greater thrust et al. Ballistic missiles launched from altitudes and indeed all types of rockets gain range or can use lower energy launched at altitudes exceeding 10,000 ft.
These days with ER projectiles, rockets, quite a few goals can be achieved at reasonable distances, if we can eliminate aerial threats to these assets. Example, I think much of the assets of the PA can be within sustained firing ranges of artillery launched from within our side of the border/LoC. Throw like a million shells at them, it is only a billion dollars and will damage much of their assets and quite a few of their cities too, including Muzaraffabad, Pind, Ibad, Lahore, Muridke and if needed a few more in Sindh too.
Dispense 100,00 shells a day, the entire action can be completed by 1000 guns under an hour. Also no, it is not outrageous, the US for example dispensed an average of 10,0000 shells per day in Vietnam. It will certainly be enough to harass them and destroy maybe 20% of their assets enough to brown lungis. In contrast, at Kargil we dispensed less than 5,000 of these sweeties (including mortar). The airforce and precision strike will have to suppress any counter fire. What do we call this strategy?
If the pukes have the guts to escalate let them. If for every terrorist incident, we throw a thousand 155 mm shells at one of their cities, they will get the message. All this small arms fire and 81 mm is playing their game of tit for tat and does not achieve much.
I am in awe of the 2nd artillery of the PLA and hence do think we need mountain guns in spades, along with loads of Brahmos, Pragatis, Prahaars and conventional Prithvis, in addition to maintaining superiority in the air on the Tibet border. If we can mange to keep the upcoming ATAGS under 12 tons, it would be heli lift capable. Our ability to deter the PLA depends upon air and fire power superiority, that we can assemble on the border.