German Rifles should have slightly more damage (by like a point), less damage dropoff, more accuracy, and heavier recoil. All rifles should be able to use clips unless they have a scope that interferes with the charger.
All weapons that share the same ammunition should do the same damage, just the range and accuracy are different.
The Soviets should get 71-round SMGs (even if that means unlocking them at a higher level than the Huns), specifically the PPD-40 and the PPSh-41, and remove the PPD-34/38 from being unlockable and replace the Premium Squad’s PPK-41s with PPD-34/38s or NKVD Thompson. If you want to nerf the SMGs with Drums just give them one reload and that’s it. The Soviet SMGs had ridiculous RoFs (with 800rpm for the PPD-40 and 1,200 for the PPSh-41) so that ammo will zip away in seconds. The PPSh-41 should also have some rather horrific muzzle flash. The German MP-28 should have slightly more horizontal recoil to the left. The MP-38/40 and the PPD-40 should both have comparatively similar unstableness due to lack of a compensator on the PPD-40 and the stocks of the MP-38/40s being frankly rather rotten creatures.
The Madsen should be a German LMG and it should be one of the 8x58mmR Danish ones, the 6.5x55 Krag ones, or the 8mm Mauser ones. The only LMG the Soviets should get is the DP-28.
The MG-42 on a sandbag should be replaced with a Maxim 1910 with a shield on a carriage mount/DShK on a Tripod for the Russians and a MG-08 With a shield on a sled mount/MG-34 on a Tripod for the Germans (or even better make it customizable). The Watercooled MGs could have lower RoFs and less visibility for no overheating and better protection. Emplaced Machine Guns Should have to be reloaded every 250 rounds, unless it’s the DShK which it should be reloaded every 50 rounds.
There should be more grenades for both sides.
The Soviet helmet should have a higher chance of bouncing shots then the German one but protect less. The Soviet Assault Squads (and if they add border guards, them too) should be able to get SN-38/SN-40 armor, both of which are extremely rare drops from logistics. Helmets should be equippable and be fairly common drops from logistics. Gas Masks should be equippable cosmetics.
Pretty much every full sized rifle calibre round has the exact same cavitation properties as each other. They all contain a huge amount of energy and cause similar amounts of internal damage. Really the damage of all of them should be the same. The only reason I think the German rifles are doing less damage than the Russians ones is because the Russians have a lower win rate and the devs are trying anything they can to even it out. Even with the worse weapons the Germans are still winning more.
Also I don’t know where you got the idea of a 1200 RPM PPSH but the vast majority of them fire under 1000 rpm.
Also I don’t think they should simulate helmets working really. Yes early soviet helmets were very good at stopping pistol calibre rounds. But even they couldn’t stop 7.62x25 and even a German helmet could stop a 9mm round at about 10m fired from a handgun. In both cases “stop” is slightly exaggerating as while they don’t penetrate the size of the dent is massive and you’d still end up with a broken skull.
I thought the PPSh-41 had a firerate of about 1200 rpm, also that is a good point about the helmets stopping bullets but still killing the wearer.