Honestly, given the speed that Karakurts are going into production, I would bet all those vessels that might need these new 76mm guns will be retired and replaced by then.
Depends on how long they want to keep their older vessels in service for... there is still a gap with larger vessels anyway so keeping a few extra lighter vessels makes sense.
These new corvettes can perform many missions previously performed by Frigates or larger vessels so the new corvettes can supplement the older larger vessels while the older corvettes continue the work they are doing for a bit longer.
Or they can do like Israeli and put on some of them Tor missiles instead of the big gun.
Would prefer them to put both big guns and missiles on their ships. The whole focus is standardisation, so arming some with missiles and some with guns defeats the purpose of standardisation.
Newer missiles are much more capable than older models so not having ten times more missiles is not as bad as it appears.
In fact, replacing guns with AA missiles and old AShM with Urans on those Soviet era boats would be very quick and cost effective option. Small ships like those don't really need guns since these days they will be used as support for other vessels anyway.
Combat experience seems to suggest that having more guns is better and not worse. After the Falklands war Soviet vessels were noted to have a lot more HMG positions around the super structure and bridges... I doubt taking away medium and heavy guns is a good idea.
Just like I think it is important to keep a 30mm cannon on the PAK FA, Su-35, and MiG-35.
Clear for me. Since it's lighter, it can be mounted on lighter vessels.
The Soviets/Russians already fitted light vessels with heavy guns... the Pauk class for example would probably have had a 57mm gun if it was a western development.
The new gun mounts means they can fit 100mm guns in ships that previously carried 76.2mm guns already.
... but not ships like Molniya/Tarantul-class corvettes and older Ropucha-class landing ships, which are/will be nearing decommissioning.
For ships serving 5-10 or more years it makes sense... for ships about to be scrapped of course it makes no sense.
Well, a quick-firing 57mm gun like the Mk 110 made by BAE Systems, with airburst ammo would do the job quite good as well, a 76mm would be quite an overkill against a small motorboat.
Anything too small to be engaged by a 76.2mm gun can be engaged with 30mm or small arms fire.
since there are plenty of Tarantul and Grisha corvettes to replace.
They likely wont replace old models one for one...
In my opinion, an AK-630M2 "Duet" (which Buyan-M corvettes already have), and a naval version of the Tor SAM system (not the "Kinzhal" one) would be enough for Karakurts and Buyans,
I agree, but I think a medium calibre gun is more useful than just adding more missiles. The latest model of the TOR system is rather capable...