I bet it has a brutal recoil.
Roger that. I've got a very small Kimber RCP, and while it's an excellent carry pistol, it's an unpleasant little bugger to shoot. There's no weight to catch any of the recoil. It all goes into your hand.
Picture
http://www.gunauction.com/search/displayitem.cfm?itemnum=7654553
Oddly the Detonics 45acp had mild recoil.
Picture
http://www.handgunsmag.com/2010/09/24/featured_handguns_master_121305/
This weapon in the article is basically a Derringer. I guess the recoil is similar.
The law of conservation of momentum guarantees it. A gun which had the same mass as the bullet would result in the gun being propelled backwards with the same speed as the bullet going forward. This thing would NOT be fun to shoot.