Accurate determination of burning characteristics of the propellant and thermo-mechanical loads acting on the barrel supports better gun design and its tactical use. As the frequency of successive shots changes, burning rate of the gun propellant also changes and consequently the bullet velocity and internal pressure of the barrel changes as well. In this work, combustion characteristics of double base propellants with various grain sizes and initial temperatures were determined by performing a series of shooting tests and employing a thermo-mechanical model with ABAQUS (R) finite element code. Effects of various grain sizes (300-425, 425-500, 500-600, 600-710, 710-850 mu m) and initial temperatures (-60, 20, 0, 20, and 60 degrees C) of double base propellants on internal pressure, bullet velocity and barrel heat transfer were investigated experimentally and computationally. Samples of propellants were tested in a shooting range by using a NATO standard small caliber barrel of 7.62 mm in diameter, and barrel internal pressure, bullet velocity and barrel surface temperatures were measured experimentally. The barrel experienced high thermal stresses during the shootings. Based on the comparisons between the simulations and the experiments, the finite element model was in agreement with the data within 90% accuracy. (C) 2016 Elsevier Ltd. All rights reserved.