K-4 is a Post Boost-Phase Vehicle (PBV) designed to perform exo-atmospheric corrections before deploying MIRVs and submunitions at borderline IRBM ranges. IISS estimated its range to be 3200 KM for 600 Kg of submunitions or if the warhead is MIRVed.
If you remember, before K-4 was K-2, an endoatmospheric MaRV with very low CEP. Either it was produced silently and kept in some numbers or IRGCAF just gave up on the MaRV idea and went for PBV-submunition or possible MIRV. May be they saw no utility of an accurate strike at such longer ranges.
I don’t believe Iran has MIRV bus technology or if it does it’s not been shown off. I believe there was an animation video from Iran that showed the K-4 bus and none of the warheads had fins thus pointing to MRV not MIRV.
Thus I think K-4 is MRV (multiple re-entry vehicle) and not MIRV (multiple independent targetable RV). I don’t think any missile exists in the world that releases MIRVs that are not nuclear warheads. It’s expensive tech to pack 3 warheads that each have the ability to target different points only to have them carry a conventional payload.
I think until sufficient evidence is released we have to assume K-4 releases FINLESS warheads after aligning the PBV in the [late] exo atmospheric phase prior to re entry and that was also what that animation showed. If that is case then CEP could be quite large (500meters+) and making the weapon for use on either civilian centers, ports, large military bases/airfields, large economic targets (power plants, water facilities, etc).
You are correct about K-2 there was a variant with a warhead similar to Emad, however that warhead was smaller than the traditional warhead and thus couldn’t carry a max payload like you see in K-4.
I agree with your theory K-2 with MarV was likely not adopted, my thoughts are cost wise and Emad was likely much cheaper vs the “newer” Khorramshar family engines. Why have two liquid missiles doing the same job?
There isn’t a lot of Intel on what the differences between K-1, K-2, and K-3 are. I know there was a poster once showing K-1 & K-2 stats, but K-3 I don’t ever remember being unveiled. It makes me wonder if K-1 thru 3 were different working prototypes and ultimately K-4 was the mass produced variant.