IITM at DEFEXPO 2020 plans to showcase a project to develop ramjet powered 155mm shell under Lt.Gen P. R. Shankar(Retd), who is now teaching at IITM.
It will have over 70KM range. The idea is to Indianize the Very Long Range Precision Fire program of US Army.
I suggested on twitter to develop as an interim a modification to the base bleed motor with nozzles to develop thrust or develop a more energetic propellant with existing base bleed motor.Base Bleed technology
Most (50–60%) of the drag on an artillery shell comes from the nose of the shell, as it pushes the air out of its way at supersonic speeds. Shaping the shell properly can reduce this drag but it is difficult to remove.
However, another powerful source of drag is the low-pressure area left behind the shell due to its blunt base. Base bleed can reduce this drag without extending the base of the shell. Instead, a small ring of metal extends just past the base, and the area in the rear of the shell is filled with a small gas generator. The gas generator provides little to no thrust, but fills the vacuum in the area behind the shell with an inflow of gas, dramatically reducing the drag. The lessened turbulence also turned out to produce tighter grouping due to the projectiles having a more consistent trajectory. The only disadvantage, apart from a higher price per shell, was a small loss in explosive payload in older shells due to some of the space inside the shell being taken up by this mechanism, but modern gas-generators are both smaller and incorporated in the shell casing.
So a more energetic propellant and/or redesigning the straight vents to have venturi effect would add thrust.
This would require reducing the number of vents to accommodate the larger diameter of the nozzle vent. Currently shows twelve vents. Might have to go with 6 to 8 vents.
A pyramid drill or boring bit can do the modification quite easily.