I have been looking at some of the S&W models and came across the 340 PD, 640 and a few others without hammers.  What is the real benefit to this aside from the hammer potentially digging into your side?  Any problems with the lack of a hammer that wouldnt be encountered if there was one?  Any general info on why you would want this over a regular revolver?

Quoted: Several advantages on the hammerless design. 2) Should you need to, you could fire from inside your coat pocket. (Not recommended for pants pockets.   )

That's THE reason I like 'em

Quoted: I have been looking at some of the S&W models and came across the 340 PD, 640 and a few others without hammers.  What is the real benefit to this aside from the hammer potentially digging into your side?  Any problems with the lack of a hammer that wouldnt be encountered if there was one?  Any general info on why you would want this over a regular revolver?

The advantage is the snag free design.

The major disadvantage is that you have to slightly stage (pull) the trigger to rotate the cylinder in order to perform a *high primer check*. The high primer check is done to ensure that none of the cartridges have a poorly seated (high) primer that could bind up the cylinder.

IMHO the Bodyguard is a superior design providing the same snag free advantage but also allowing a high primer check by slightly pulling back on the hammer as opposed to the trigger. It's obviously much safer to perform the high primer check using the hammer vs. the trigger.

I suppose you could *pre check* your premium carry ammo for high primers but that's not practical for general practice or a training course where you'll be shooting hundreds of rounds.

I will say that I, for one, have never liked the M38 / 638 Bodyguard design and much prefer the M40 / 642 style guns for my personal use. TonyF is correct about staging the trigger, but that is not a big deal once you get the hang of it. The 640/642/340 design allows a higher grip on the backstrap, which gives better control for follow up shots, lets no lint or other crud inside, and hides much better in a pocket IMO.

Quoted: TonyF is correct about staging the trigger, but that is not a big deal once you get the hang of it.

That may be true but at least one instructor I know frequently sees ND's when students run centennial's in his classes. The other thing is that we're violating Rule #3. And I know it's convenient but I never liked pocket carry. To each his own I suppose.

Thanks for the tip in the other thread.

One thing to be very careful with in these little guns is spring tension. Since the mass of the moving parts is less, the mainspring and trigger return spring need to be left at or very near to full factory strength. Yes, they are on the heavy side, but these are no-shit close range self defense guns and MUST go "bang" for every shot. Do NOT allow some "gunsmith" to do an "action job" that will compromise your safety!

Smooth is good...light is not!