Simulation time: 30 mins, Render time 2h 15 mins, Xeon E5-2670.
10M cells, Units scale = 0.02 meters, Symmetric Conservation, Q=50, Multi-pass advection, SPF=3.0, Vorticity xV = 0.5, Cooling = 0.2, Smoke dissipation = 0.05, Randomize Amount = 0.5, the rest are defaults. Default render settings too, except for External scatter boost = 0.8. The shell object velocity multiplier is 4.0. Gun discharge is 100K for 1 frame, Shell discharge is 30K to 0 in 4 frames. Ground smoke is brushed and has temperature of 270 to make it heavy (below 300).