A melt castable General Purpose (GP) Insensitive High Explosive (IHE) formulation was developed and subjected to a number of performance and sensitivity tests. The formulation consisted of a thermoplastic binder with 3-nitro-1,2,4-triazol-5-one (NTO) as the primary insensitive explosive. Other ingredients include: aluminum powder (Al), ammonium perchlorate (AP) and cyclotrimethylenetrinitramine (RDX). The detonation velocity of the explosive was measured at 7080 m/s at a density of 1.79 g/cm(3) at a confined diameter of 20.3 cm. This paper is concerned with the fast cook-off (FCO) thermal sensitivity response of this composition (identified as TE-T7005) in a large scale/heavily confined test apparatus to simulate large storage quantities.