AFX-757 is an insensitive high explosive developed by the Energetic Materials Branch of the U.S. Air Force Research Laboratory. Initially, it was intended as a replacement for the tritonal filler of hard target penetrator bombs, but has found other applications. It is a mixture of RDX, aluminium powder, ammonium perchlorate and the plasticizer hydroxyl-terminated polybutadiene (HTPB).
AFX-757, which is cast-filled into warheads, has been used in warheads including the 250lb GBU-39/B Small Diameter Bomb, the WDU-42/B warhead of the AGM-158 Joint Air-to-Surface Standoff Missile (JASSM), BLU-121A/B 2000lb penetrator bomb with thermobaric effects, and BLU-122/B 5000lb hard target penetrator. As part of the JASSM project, it was the first explosive certified in the lowest hazard category for transportation, essentially stating that it will not explode accidentally. 
- Insensitive High Explosives, Globalsecurity
- Solicitation Number: W15QKN-09-X-1211, Removing Cast-Cured Explosive Fills from Military Munitions, Department of the Army, 30 June 2009
- "JASSM Subjected to Insensitive Munitions/Hazard Classification Tests - IM/HC - weapons systems", Program Manager, November 2000