i don't think any AAA have 5km range IRL to match the range of rockets nor ATGMs
Gepard is claimed to have 5km effective range.
Tunguska - 4km.
Even Shilka can scare off helos at 4km as the shells can fly so far, only that the accuracy would be abyssmal. Though even it has 2.5km effective range. NATO helo pilots didn't cared a lot about SAMs, but a Shilka - it's a living nightmare.
It's been pointed out a lot - most weapon systems have ranges reduced to 'effective' ranges, and only AAA is reduced to half it's effective range or even lower.
I would suggest to make it so:
Top of the line AAA (Tunguska, Gepard, Veak-40 (?)) - 2800m. ZSU-57 can also be in that range.
Average (Shilka, Vulcan, etc) - 2400-2600.
Low-tech (ZU-23-2 and so on) - ~2000.
That shows quite nicely that things like ZSU-23-2 are situational 'ambush' weapons mainly, while Shilkas and co can counter helicopters with rocket weaponry (as they were designed to do IRL) and modern SPAAGs can also be quite dangerous even to ATGM-armed helicopters - as they were designed with such a threat in mind.