A gas generating composition (GGC) was designed with Guanidinium azotetrazolate (GZT) as fuel and Ammonium perchlorate (AP) as an oxidizer for burst testing of nozzle closure at rig level, simulating solid rocket motor ignition transient and propellant flame temperature. EXPLO5 software code was used for formulation studies. The selected GGC formulation was subjected to thermokinetic analysis for understanding the thermal decomposition behaviour as well as evaluating kinetic and thermodynamic parameters of decomposition. The non-isothermal kinetic parameters of the composition over the extent of conversion were determined using two isocoversional methods viz; Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS). GGC in pellet form was fired using a pyrotechnic pressure generating device (PPG) in test rig level with nozzle closure. The nozzle closure was burst opened at a pressure of 0.985 MPa with a pressurization rate of 10.3 MPa s(-1).