This slug (Commission Exhibit 399) is the projectile which the Warren Commission
asserted was the cause of several wounds in both President Kennedy and Governor Connally.
It is virtually undamaged (click to enlarge).
Similar bullets test-fired into solid objects were greatly misshapen. The photo below (HSCA -JFK exhibit F-294) shows CE 399 at far left. The second and third slugs were test-fired into tubes of cotton and show slightly more distortion than CE 399, which supposedly passed through both men before striking Gov. Connaly's wrist and lodging in his leg. CE 856, at far right, was fired into the wrist of a cadaver. Notice the damage from this single impact.
These images and more can be found at http://www.jfk-info.com/fragment.htm.