Abstract: A telescopic penetrator composed of long rod and long tube is designedto solve the problems caused by slenderprojectile (large length / diameter ratio). By means of experimentsand numerical simulations, the performancesof long tube and long rod with the same mass and length in the samematerial normally against semi-infiniteRHA(rolled homogeneous armor) are compared. The penetration patterns ofthe long tube and long rod aredescribed. The relationships of velocity vs. time andmass vs. time for two kinds of penetratorsare also obtained. Both the experimental and the numericalresults indicate that thedecreasing rates of long tubular velocityand mass are greater than that of long rod in the penetration course.Therefore, the penetrationperformance of the long tube is inferior to that of the long rod.