A reporter reminded me earlier of the Remington XP-100 long range pistol, a predecessor to the Contender. They started at .221 but could take a new barrel up to .45.
Here's something interesting I found on the web about this very subject,
http://www.snipercountry.com/higrnd09.htm
The Sniper Pistol -- A Tactical Alternative
FYI-Looks like ;some LEO are finally considering a "smaller" weapon.