Ok, “How many shells were fired in the opening megabarrage of a multi-front offensive operation, such as a Fuldapocalypse or All Union’s invasion of Romania?”

Going with the latter because it’s my book, I finally have an answer that’s easier than a vague “Over a million.” Going with “Sustainability of the Soviet Army In Battle” and “Front Operations 1977” as main sources.

A unit of fire for each artillery piece translates to about 80 for 120-122mm, 60 for 152mm, 160 for BM-21s, and 120 for smaller mortars (sust., pg 68). GENFORCE Mobile has similar numbers but adds 40 for big 203+mm pieces. I’ll just split the difference and say 70.

“Thus, for instance, in armies operating on the axis of the main attack, the expenditure of artillery and mortar ammunition in the first day of combat actions without the use of nuclear weapons may be 2.0 to 2.5 units of fire” (front. pg 309)

A front is described in the same document as having 3,400 to 4,200 artillery pieces (front pg. 12), so a very basic napkin calc for two fronts gives 1,176,000 shells. That’s about 25,000 tons even if you assume “only” the weight of a D-30 round for each shell.

So yeah, 100-150 x the number of total artillery pieces for an extremely basic ballpark figure.