as that shown at 74 on core member 60 can be engaged by a screw driver in order to screw the core members into or out of jacket 12 it is possible to remove any one or all of the core members if desired it is of course possible to modify any of the core members by changing the length of the stem the length of threaded portion of the core member or length of both the stem and the threaded portion for example one may lengthen the stem of core member 60 so that it seats snugly in counterbore 70 or one could lengthen the threaded portion of core member 56 until it reached rearward end 22 of the projectile the chief advantages of the fig6 embodiment are the ability to adjust the weight of a projectile and to move the center of gravity of the projectile along axis 24 by using different orders and combinations of core members generally speaking moving the center of gravity forward in a spinning projectile causes the projectile to be more stable in flight and moving the center of gravity rearward tends to make the projectile tumble either in flight or upon striking a target both greater stability in flight and tumbling can be advantages depending upon the target 39 s distance and character it is contemplated that the half jacket embodiment of my projectile shown in fig6 could be modified to have removable core members such as core member 60 so that the fig6 embodiment coudl have an adjustable weight and center of gravity dashed line 76 in fig6 represents the location and orientation of a rifling.