Abstract: The loading precision of projectiles and the consistency of bore jamming of large caliber barrel have a great impact on the bore wear and firing accuracy. Based on the bore jamming status of large caliber projectile, a nondestructive measuring method is presented for measuring the geometric parameters of projectile muzzle in firing field. The measurement principle and system composition of the measuring method are introduced. The measurement models of the axis of chamber, the axis of projectile and the tail end of projectile are established, and the performance of each measurement module is analyzed and verified. On this basis, the geometric parameters of projectile are measured by the proposed measuring system. The stability and accuracy of the measuring system are verified through the analysis of the experimental results. Key

Key words: ordnancescienceandtechnology, borejamming, attitudetest, coordinatetransformation, displacementmeasurement, obliquity