There have been some related threads on this subject recently.
Here is my reply to one of them:
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I like the S&W Bodyguard Airweight, Model 638, with the "humped back", shrouded hammer.
For me, it offers the best of both worlds....you can still cock the hammer, if required, for a longer range emergency shot.
Also, you can perform a cylinder rotation check....You may think that the cylinder will never bind, but it has happened to me. (The dirt, dust, and lint that will get into your gun in ankle carry makes binding all the more possible.)
The Model 638 has the snag-free qualities of the enclosed-hammer, Centenial series:
1) It will not hang-up on the draw due to your hammer catching on clothing.
2) It can be fired from inside, and through a jacket pocket or a woman's purse.
-Mk.IV
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The threads can be found at:
http://www.pistolsmith.com/viewtopic.php?topic=362&forum=16&25
http://www.thefiringline.com/forums/showthread.php?threadid=67691
http://www.thefiringline.com/forums/showthread.php?threadid=66599