Important S-400 news. @halmiso1 spotted that both the 93rd and the 1529th Anti-Aircraft Missile Regiments have 51P6A TELs in addition to 5P85SM2-01. This is significant because only the 51P6A is believed to be capable of employing the long-range 40N6 400km range missile. 
Russian OPK sources told TASS back in the fall of 2018 that the 40N6 missile was operational, but we never saw the missile on display nor saw any public live fire demonstrations. 2/
Last September, the Russian MoD spokesman Igor Konashenkov said that the max range of Russian air defenses in Syria was 250km, which is consistent with the max range of the 48N6DM/48N6E3 missile but not the 40N6. 3/
40N6E missiles were supposedly part of the export agreement with China (though we haven't seen them), and Turkey received 8 51P6A/E TELs as part of its first (and possibly last) S-400 regiment. 4/
51P6A/E TELs are also the only S-400 TELs that can apparently employ the shorter-range 9M96-series missiles. 5/
But Russia is also procuring the S-350 Vityaz air defense system that is equipped with that missile. So the appearance of 51P6A TELs in Russian S-400 units possibly indicates that the 40N6 has actually been adopted and will be delivered to operational air defense units. 6/
This means those S-400 bubble maps that show a 400km max effective range may soon be accurate. Though it is important to point out that that range is only possible against aircraft flying at high altitudes and mostly AWACS. The max range against low-flying fighters is smaller. 7/
