Fully tapered jacket ruptures instantly at the thin jacket mouth, yet the gradual thickening along the bullet's axis controls expansion and curls the jacket uniformly outward, at high or low velocities. Special lead alloy dual core construction provides superior mushrooming characteristics at virtually all impact velocities. Integral partition supports the expanded mushroom and retains the rear lead alloy core. Enclosed rear core retains more than half the original bullet weight for deep penetration. Special crimp locks in the rear core section, adding strength to resist deformation under the pressure of heavy magnums.