The Federal Bureau of Investigation (FBI) awarded Winchester Ammunition its coveted ammunition contract for 9mm pistols. The Winchester PDX1 will be the Bureau's service round, and its SF Frangibles cartridges will be the Bureau's training ammunition. The FBI has selected Glock Gen 5 pistols in 9mm as a service weapon. There has been much speculation about the reasons for its change in calibre.
There's a short answer, science. They did the research and they did the calculations. A common choice for law enforcement agencies, this 9mm ammunition has scored well in independent and FBI ballistic tests. The Federal HST LE bullet is designed to expand and create a large wound cavity.
At the lower gun cartridge speeds, the temporary cavity is not produced with sufficient speed to have a wound effect; therefore, any difference in the temporal cavity observed between the calibers of the guns is irrelevant. Due to the elastic nature of most human tissues and the low velocity of gun projectiles relative to rifle projectiles, medical professionals, experienced in evaluating gunshot wounds, have long established that damage along the trajectory of the visible wound in autopsy or during surgery cannot distinguish between common gun calibers used in law enforcement. Fragmentation does not occur reliably in gun wounds of soft tissues due to low gun bullet velocities.