Actually every single AT gun in the game has a 6 man crew, if the soviet man it. As such its faction trait and not a gun trait. You can't balance team weapons that can be crewed by anyone with the trait of that faction in mind because you end up with things like the maxim that is absolutely without value UNLESS you have a 6 man crew.
The zis pays for the barrage with inferior AT stats, which believe it or not, is why people buy AT guns.
Soviet weapons in general seem to pay for inferior stats with increased utilities (this helps offset the 6 man crew in a way but ensures that the weapon has value without the crew despite the lower stats, something the maxim notably misses as an example)
Also. The OTHER soviet AT gun also deals AI damage and has a 6 man crew following with the above reasoning but also disqualifying your complaint entirely.
Doesn't disqualify at all just shows soviet has a lot of firepower in every single AT-gun they can wield and we aren't talking about 45mm which is behind commander pick. 6 man crew being soviet trait is already known, doesn't still change that it's 6 man crew with the bonus survivability that brings (And I am not even talking about it at all). Back to barrage, they already have it on su-76 where it should be. Anyway people getting so damn touchy if brought small change and balance to the game. I never said to remove barrage from Zis and was only suggesting hide it behind veterancy so it's not a no-brainer build for soviet and gets no punishment for making it if Axis player goes heavily in infantry and not make a light vehicle play at all. If veterancy feels too high change then increase in munition cost is needed as at the moment it's pretty spammable ability for AT-gun doing things that normally isn't meant to do in this game for any faction, this is still my opinion. You want to barrage, build a mortar, build artillery, build even Su-76 where this ability should only be.