Interestingly, the US does not buy artillery shells from the corporate defense sector, but instead produces them in government-owned munitions plants. (Albeit a contractor is apparently hired to operate the taxpayer-owned plants.)
Anyhow, at the start of the war these American armories were making 14,000 155 mm artillery rounds.
After the war started the US Army invested $1.45 billion to expand the production capacity. (It is not clear to me if this money was allocated in May 2022 or December 2022. The latter seems likelier.)
The result was that by October 2023 the production had doubled to 28,000 rounds monthly.
In November 2023 the Army allocated a further $1.5 billion to invest in capacity.
And the passing of the “Ukraine aid” bill last week allocates yet another $3.1 billion to expand production.
Some of the money will go toward building an entirely new ammunition plant in Texas that will be the most automated to date.
On October 2023 Army said it was planning to be building roughly 37 thousand rounds per month by April 2024, 60 thousand by October 2024, and 100 thousand by October 2025.
Thus 18 months from now the US will be producing over 3300 rounds daily.
Some of these will go toward replenishing the partly depleted US stockpile, but I predict that as long as the war rages the majority will be going to Ukraine.
Currently Russia fires about 6000 artillery rounds daily, while the Ukrainians are back to firing just 1000. (They were firing up to 5000-6000 themselves during their attempted 2023 offensive.)
As we have seen this is a temporary state of affairs. US capacity to supply Ukraine with shells is increasing quite rapidly. The EU has been slower in ramping up, but its capacity is rising as well.
Some two years from now the Ukrainians could themselves be firing 5000 rounds daily.
By failing to knock out Ukraine quickly, Russia has granted Washington the opportunity to beef up Kiev and greatly intensify the fratricidal Slavic slaughter.