Effects of erosion phenomenon on the performance of a given gun barrel have been analyzed throughout numerical and experimental studies. Mainly, qualitative observations were performed. Theoretical relations between the evolution of the inner barrel profile and the provided interior ballistics are limited. This article focuses on the development of a numerical model to predict the engraving resistance evolution in terms of the inner barrel profile in the different weapon's life stages. Four test barrels “12.7 × 99 mm NATO” with different chamber volumes were considered. First, a Coordinate Measuring Machine (CMM) with a contact scanning probe was used to measure the inner dimension of the guns. Second, piezoelectric sensors with a special Doppler radar were considered to measure the (i) pressure and (ii) the bullet velocity in the test weapons. Finally, based on the obtained experimental results, a finite element (FE) analysis using the commercial software LS-DYNA was developed and validated. The obtained numerical results were used as insights to quantify the relationship between the engraving resistance and the chamber volume of small caliber guns.