410 bore Winchester 410 bore 3” shell, 5 pellets of unplated 000 buckshot Barrel was a break-action, 18” smoothbore Mean pellet impact velocity was 1107 ± 0.500 ft/sec Average penetration was 18 ± 0.031” Block calibrated at 612 ± 0.500 ft/sec and 9.3 ± 0.05cm penetration Curiously, the temporary cavity on this round never seemed to collapse from its approximately 1.5 ± 0.031” diameter magnitude, for the entire length of the 16.0 ± 0.031” block. All rifle and pistol projectiles seem to create a temporary cavity at the initial inches of penetration and then collapse to the size of the permanent cavity. This load produced an approximate 16”x1.5” diameter temporary cavity.