The 76mm armed Sherman was not compatible with the Russian 76.2mm shell. Those tanks were sent because the Russians considered the 75mm woefully underpowered, which by the way was absolutely correct.
I would like some proof that there was production of Russian shelltypes in the US. For instance an image of crates saying "Contains 122mm shells" ect ect. Anything beyond a list that says certain chemicals were sent (which by the way lacks cordite, the main explosive of artillery).
I find it hard to believe that whole factories would be dedicated to the Russian wareffort, since everything else I have seen has been either compatible equipment (equipment used bythe US itself) or general equipment (Jeeps, locomotives, food, rolled metal plates and so on). The US worker would be furious that he would be working for the SU while his own boy was fighting and dying in Europe or the Pacific. He would not like that his work would not be able to help his boy directly, but rather help communists, whom he certainly didn't trust.