An apparatus for conducting a small-scale shock reactivity and internal blast test (SSBT), and a related test method that simulates a large scale test of explosive materials while employing small quantities of materials for the characterization. The apparatus includes a small scale shock reactivity test (SSRT) device, and an internal blast test device including a pressure chamber with an accessible interior, a pressure transducer, a multipurpose port provides an electrical connection to the shock reactivity test device, and a small gas port. The SSRT device is housed within the pressure chamber, and gases and materials produced during a small scale shock reactivity test are quasi-statically retained by the pressure chamber. The pressure transducer is in communication with an instrument that can display the pressure detected in the pressure chamber for analysis.