In Ukraine as in previous major conflicts artillery is the biggest killer on the battlefield, accounting for perhaps 80% of casualties on both sides. But while Ukraine has fewer guns firing fewer shells, they appear to be doing more damage even though, with some notable exceptions, they are using the same weapons as their Russian opponents. How is this possible?
A Msta-SM self-propelled howitzer fires during a field show at Patriot Park as part of the Army 2020 International Military Technical Forum. Sergei Fadeichev/TASS/Russian State Media.
The Numbers Game
Russia has enjoyed a huge advantage in artillery since the start of the invasion with roughly twice as many guns and MRLs, and more importantly, massive stockpiles of ammunition. Figures vary wildly, and have changed over time, but all put Russian substantially ahead in terms of shells fired.
In November NBC quoted US officials estimating Russian expenditure of 20,000 rounds per day against 4,000–7,000 for Ukraine. NATO Secretary General Jens Stoltenberg stated in February that Russia was firing around four times as many shells as Ukraine. In March, Spanish newspaper El Pais quoted EU insider sources as saying that Russia was firing 40–50,000 rounds per day, compared to 5,000–6,000 for Ukraine, while Estonia (which has supplied shells to Ukraine) estimated that Russia was firing 20,000–60,000 per day compared to 2,000–7,000 from Ukraine. 
So Russia is likely firing something between four and nine times as many shells as Ukraine.
And yet, Russia has suffered much higher casualties. To take just one figure, recently leaked Pentagon documents suggest 189,500–223,000 Russians killed or injured compared to 124,500–131,000 Ukrainians or 1.4 to 1.8 to 1. 
Much of this can be accounted for by the fact that Russia’s campaign has largely been on the offensive, while Ukraine has largely been on the defensive. Yet, for long periods we have seen largely static warfare. Russia’s advantage in artillery should have been reflected in casualty figures, …