There are enough 40 caliber pistols out there that ammo may well never be in short supply, but 357 Sig and 45 GAP ammo could be a problem in a few years. The real data says different. Prior to 1994 our city PD carried Smith 66 revolvers loaded with 38+P+ ammo. The county PD and Sheriff's deputies carried personal guns and could carry anything they could qualify with. In 1994 the city issued Smith 5906's in 9mm, the county PD and Sheriff's office G22's in 40 S&W. Since then there have been 14 LE involved shootings. Seven with 9mm, six with 40 S&W and one where both were used. In every case but one the officer fired 2 quick shots and the bad guy was dead in their tracks. There have been no survivors, no more than 2 shots fired and realistically one would have probably been enough. The one where more than 2 shots were fired involved a person who took police on a 25 mile chase before being forced to stop. They then refused to get out of the car. When LE broke a window to pull the person out the person pulled a gun and got off 1 shot at officers. Four officers from 3 different agencies returned fire with 3 shots each within just a couple of seconds. Three years ago our Sheriff's department moved to 9mm, but before doing so the Sheriff did a lot of research by contacting other agencies who had made the switch from 40 to 9mm. They couldn't find a single LE agency who had seen any difference in effectiveness.