OVERVIEW: The SS-N-12 Mod 2 SANDBOX (P-1000 VULCAN) is a long-range, turbojet-powered supersonic surface-to-surface anti-ship missile with an active radar.  It has a 750-1000kg high explosive and possibly a 350 kt nuclear warhead. 
 
DETAILS:  Some sources claim it is a variant of the P-500 Bazalt / SS-N-12 Sandbox but the missile is internally sufficiently different to be classed as a unique design.

NOTES:Russian sources claim the extensive use of Titanium structure and reduced armour, to provide reduced structural weight and increased range.  Four Echo II SSGNs were retrofitted to carry the P-1000 during the last decade of the Cold War. The weapon was installed on at least one Slava class cruiser, replacing the P-500 Bazalt / SS-N-12 Sandbox.

SOURCES: Air Power Australia. "Soviet/Russian Cruise Missiles." Accessed December 1, 2013. http://www.ausairpower.net/APA-Rus-Cruise-Missiles.html#mozTocId225318:
