The smallest, best known centerfire handgun round is the .25 caliber (or 6.35mm). The practicality of the .25cal is questionable: you have all of the costs of a centerfire round, with not much more energy than a .22LR rimfire. In fact, nowadays, you are much more likely to find .22LR pistols than a .25cal. One step up from the .25cal is the .32 caliber. This is just about as out-dated as the .25cal, but there were some very popular weapons in .32 caliber, the Walther PPK (James Bond's weapon of choice) is said to be a .32cal (not a .380ACP). There are also pistols made to shoot rifle (long gun) rounds. These tend to be smaller caliber than a .25 cal, but are fairly modern (like a pistol designed to fire .17cal HMR).
Not really.
25-85 USD or so
I have one
Proofhouse.com has Colt sn data.
Internet, gun shows, gun shop.
Yes, small game and rodents.
6, IIRC
50-450 usd
BLue Book of Gun Values
Try e-gunparts.com. Also, do a google search.
It is a type of Pistol. The link below has more information that you may be interested in.