The possibility of ascertaining approximate time of firing by utilizing the phenomenon of rate of escape of gaseous products of combustion has been investigated with special reference to 12 bore, 2 1/2 in. (6.35-mm), fired cartridges made by the Indian Ordnance Factory. The relative rate of escape of gases has been determined indirectly by ascertaining the time needed to develop color in reagents by escaping gases by diazotization and coupling reaction. It has been observed that although the time to develop color tends to increase with the time lapse after firing, the observations are not interpretable for all possible time intervals due to overlapping and insignificant increase in certain intervals. A choice of suitable time intervals may be useful in ascertaining the approximate time of firing, which may be determined experimentally in each case. Normal variation due to atmospheric conditions also may not have significant influence under certain limits. The suggested method is comparatively more useful than already existing methods.