but it should be accompagned by a boost of range for all shilkas except the afghanistanki variant to 1750 meters.
Why not the Afghanskii? It still only has a 1200 meter range against ground targets.
Because it's a ground warfare autocannon and they all seem to have 1575 meters range. I find quite ridiculous that it's actually better than the base shilka variants at firing against aircraft while it has no radar. It should be a ground support vehicule and be no better at shooting down aircrafts than the average AMX-10P.
And about the shilka being too good, it will simply bring it somewhat in the category of the vulcan while the shilka is actually almost useless presently. It's not even realistic because it was a dangerous AA gun in real life. The AA shilkas need a boost.