Do you have any more information on the 2500km range Kalibr (Klub)? I cannot seem to find information on it anywhere!
The information you read about is all about Klub and therefore about export products.
Kalibr is not for export.
Very simply the Soviet Navy developed a 2,500km range cruise missile that NATO called Sampson and gave the ASCC code of SS-N-21 Granat (Not to be confused with the 7 ton Granit of the Kirov/Oscar/Kuznetsov vessels).
250m CEP of Granat meant it was a nuke only.
Enter new technology and new terminal guidance and navigation and you end up with Kh-101 and Kh-102 terminal seeker and long range guidance fitted to the old Granit and you get Klub.
In the export family you have the subsonic all the way anti ship or land attack model with a range of about 290-300km as per international export restrictions. There is also the version with the pointy nose that flys 250km to the target at subsonic but launches a rocket powered payload the last 50-80km to penetrate the last line of defences of a ship.
The Russian versions are not limited by export restrictions so their anti ship subsonic all the way missile could easily have the 2,500km range of Granat, while their subsonic land attack missile is called Kalibr and also has a 2,500km range and a very small CEP. the main question regards the high speed missile... my personal opinion is that the subsonic section has a range of 1,000 to 1,500km with the supersonic section reaching the same 50-80km at very low altitude.
Russian domestic models are not revealed publicly and so information is occasionally slipped but confirmation is difficult.
For a while Naval officials were talking about a 5,000km range cruise missile... the Kh-101 and Kh-102 air launched missiles used by the Russian air force have this range so an upgraded ship and sub launched model is not impossible.
Plus, they are barely even on more than a couple US ships. The US is relying on the old Phalanx system instead.)
The Soviets/Russians have always taken anti ship missiles more seriously than the US or Brits... their larger ships have 8 or more gatlings and the introduction of Kashtan was largely to defend against supersonic anti ship missiles.