Just 3 random soviet weapons from Wikipedia
AI-76 /w GP-25
like the base game model in every way but has a front attechment in an underslung GL, this fires 40mmCL (caseless)
Balance wise it has two fire modes automatic and GL, swapping modes swaps you from the standard mag to a single shot GL.
comes with either a 45 round stick mag (default) or a 100 round drum (at max tier). this LMG uses 7.62 to maximum effect.
LP0-50 (a modified one that has one tank on the weapon, still has the bipod.)
A rather unique flamethrower that fires at a longer range then the resistance one but at a cost, while the resistance one can sustain fire until it is out of napalm the LPO fires only 2-3 second bursts using an ignition cartage.
Gameplay wise, this is a burst fire flamethrower with a longer range compared to the resistance flamethrower. the downside being its limited fire time at a max of 3 seconds.