A lot of early Thompsons were sent and bought by Soviet Russia and saw service in the Winter War and the Battle of Moscow before the Lend Lease Program in 1941
https://images.app.goo.gl/sweMMgJj8VQzih8K9
https://64.media.tumblr.com/f7da2ef3a3e920597698557f15f92210/tumblr_nhz9h9wGt51s57vgxo1_640.jpg
round drum https://images.app.goo.gl/qJm1Ae4joZvke1D7A
And the PPD-40 saw a lot of action in stalingrad since they never shut down production when the PPSh-41 replaced it.
So i recommend this:
In Moscow.
Add M1921 with 100 round Drum to gold order
M1921AC with 50 Round Drum to Campaign level
M1928 With 20 round box magazine to premium squad.
In Stalingrad
Add PPD-40 to campaign levels