All told, better to have fewer shells in general, but in particular, one must have at least as many shells as the murderous invaders that want to kill you.
And towards that end, the more that Ukraine destroys Russia's military, the less shells everyone else needs to build to defend themselves. Because if Ukraine falls, one only has to look on YouTube to find the translations of Russian TV that show all the other places their population is geared up to invade, rape, conquer, and subjugate.
But even aside from what happens to Ukrainians, if this goes Russia's way it will embolden many other regimes to solve their problems through fascism and colonial invasions too. Pacifism is very nice and weapons of war are absolutely an evil thing, but if you don't have them your pacifism quickly becomes appeasement and/or submission when someone who's not as nice as you decides they're gonna go ahead and institute a few changes in their neighbourhood.
Pacifism is a luxury of the extremely privileged. A very nice luxury, but a luxury nonetheless.
https://en.wikipedia.org/wiki/2014_Vrb%C4%9Btice_ammunition_...
Reading that it says 150 tons of explosives and this happened 10 years ago. So, not particularly relevant today.
2017 Balakliia, Ukraine https://en.wikipedia.org/wiki/Balakliia#2017%E2%80%932019_ar...
2017 Kalnyvka, Ukraine https://en.wikipedia.org/wiki/2017_Kalynivka_ammunition_depo...
2011, 2015, 2020 in Bulgaria https://www.thedailybeast.com/bulgaria-accuses-six-russians-...
All in preparation for the eventual invasion, in hindsight.
That the US should be giving bunker busters, predator drones, and other modern long range munitions that can end a war in days instead of years to our allies proactively as a deterrent instead of trying to fund a modern war with 20th century weapons like short range artillery.
Industrialized war is unfathomable to western powers and that's not a bad thing.
However, knowing just how hungry modern warfare is for munitions, not having the capacity already in place to vastly ramp up production seems extremely short sighted.
I think the interesting parts are everything around how it got there. How decades of focusing on expensive wonder tech and unchecked MIC grift has led to the US to this state where it fundamentally can't deliver materiel it needs. The contradictions of 30+ years of end-of-history neoliberal economics vs. the fact that someone needs to run a big potentially unprofitable factory and keep large excess inventory of if the US expects to respond to long-duration conflicts like this. Whether or not the US ends up like the western colonial empires of old sooner rather than later.
So from that standpoint 155mm shell production is an excellent window into larger trends