The current research, of armaments industry s interest, more specifically in the quality control of ammunition lots, is related to the development of methodology for calibrating piezoelectric transducers for transient pressure measurements associated with events whose duration is of the order of milliseconds. As its main contribution, this work presents proper methodology, not available yet in the Country, to ensure reliability to measurements of pressure in internal ballistics, which is the scientific study of the operating processes within the gun from at the moment when the burning process of the propellant is initiated. In spite of the low transient pressure range studied, 34,7 to 349,8 bar, when compared with the pressures developed in internal ballistics, up to 6000 bar, the simple replacement of the pressure generator for another one of larger capacity is enough to allow for calibration in a wider pressure range using the same methodology. The complex process associated to internal ballistics was simulated in laboratorial conditions by the abrupt exposure of the piezoelectric sensor, object of the calibration, planned and originally mounted in a small oil chamber (about ten times smaller than the total volume of fluid pressurized) maintained at atmospheric pressure, to a pressure peak introduced by the communication of the small chamber to a line of oil pressurized at a desired calibration pressure level by means of a hydraulical pump used to feed the oil system. Each calibration pressure condition corresponds to what is called a calibration point. Complementing the experimental apparatus used to simulate the phenomenon of the internal ballistics, an adequate measurement system (rise time < 5 us, therefore adequate to the time duration of the studied phenomenon) was used. The experimental apparatus employed is such that the time duration of the events could be changed by means of a restriction valve, allowing events with duration from about 2 to 2200 ms. Within the calibration process, the monitoring of the piezoelectric transducer output signal allowed for establishing a specific time-limit to ensure that the signal remained exempt of undesirable attenuation, considered a source of error in the measurement of the transient pressure. The calibration process was developed for 10 distinct points, totalizing 340 experiments (varying the transient pressure to which the transducer is exposed), monitoring the output signal of the transducer against the value of the pressure measured with a manometer calibrated in the accredited pressure laboratory of PUC-Rio, traceable to the national standard maintained by the Brazilian National Metrology Laboratory (INMETRO) and, therefore, ensuring overall traceability of measurements to the International System of Units (SI). Modifications introduced in the experimental apparatus used allow that calibrations usually carried out under a regime of pressurization may also be carried out under a regime of unpressurization, making possible other studies such as stability and hysteresis of the transducer s output signal. From the technical point of view the experimental method proved to be feasible and suitable to the laboratorial conditions for the pressure range to which it was validated (34,7 to 349,8 bar). It also revealed economically viable. Although validated, the uncertainty associated with the proposed method, obviously is greater than the uncertainty associated with a dead weight tester, which is based on a primary method. However, the uncertainty associated with the method of calibration herein proposed can be minimized whenever a more accurate voltage measurement system is used.