Calibers for CCW is a tough call (and this is from an LEO point of view) as
the weapon usually has to be fairly compact so as to not be detected to the untrained eye. In small to medium size towns with low crime rates, I would say that the normal, compact snubbies and small caliber semi-autos are adequate for CCW. However, that being said, if you live in a large city with a high violent crime rate and your profession requires you to spend a lot of time in a high-risk area where many of the robberies and assaults are with a firearm, then you really should consider concealing a full size weapon of at least .40 caliber. The problem with .32, .38, .380/9mm weapons is not that they don't work, they do, but if you are being assaulted by someone with a firearm and you instinctively double tap them to "center mass" as you have been trained with these small caliber weapons, you are probably going to be shot as well before your attacker collapses. With a more potent caliber with a full-length barrel, the odds are significantly higher of delivering enough shock on a "double tap" to center mass to prevent accurate return fire.