Winchester Defender ammunition was tested by the FBI to see if it can stand up to real world, life threatening situations, this ammunition has impressive expansion and notable velocities at various ranges thanks to Winchester's proprietary bonding process. The engineers have welded together the lead core and copper jacket to obtain controlled expansion and a higher weight retention. The bonding can also take on the toughest barriers at varied ranges and velocities to simulate real world threat. Upon impact, the jacketed hollow point initiates expansion up to 1-1/2 times the size of the original bullet diameter. The unique notching in the bullet creates six equal segments creating maximum expansion on impact. Finally, Winchester has chosen nickel plated brass to maximize reliability through smooth chambering and case ejection.