This is Tumble Upon Impact®
Fort Scott Munitions’®, FSM® monolithic, solid copper projectiles are specially engineered to tumble when striking water-based tissue. This Tumble Upon Impact® TUI® design ensures that the distribution of damage primarily occurs internally instead of at first contact with skin. Our ammo effectively flips end-over-end once hitting fluid, cutting through everything in its path as well as creating a larger surface area of damage.