What is the likley cause

[Sullyman]

A neighbor had an issue with his S&W .357 revolver, loaded with .38 sp (I don't know the model) His wife pulled the hammer back, the cylinder rotated. She went to let the hammer back down, pulling the trigger and easing it back down. The hammer would not go back down when pulling the trigger. The hammer was locked back with the trigger fully pulled back. Nothing would move. She set it aside for her husband to deal with. He could not get the hammer to release. So when he set it down on a table (pointing away) it went off. He was cradling the cylinder with one hand when setting it down so as not to jar it. 10 stitches later and some powder burns he is fine and the bullet went harmlessly into the woods.

What could have caused this?? He has not been able to recreate it since it happened. The revolver was newer (50-100 rounds)

 

[beag_nut]

HUH???
Can't think of any new revolver that would happen with.

 

[Garak]

My guess would be too tight tolerances and a foreign object (dirt, metal shavings) in the trigger mechanism. The handling jarred it off.

 

[dfsixstring]

"Or" we may not be getting the full story. I'm not trying to insult anyone, but I've embellished my story to my wife so as not to look like I did something dumb before.


Dfsixstring
SR9c
LCP
RST4S

 

[MrBorland]

Sounds like she got the trigger nose jammed behind the double action sear when letting the hammer down. Kind of a faux half-cock. Shouldn't happen, but the DA sear could be too long.

Hubby's messing with it got it loose, and the hammer dropped. It shouldn't have gone bang if his finger was off the trigger, though, as the hammer block would've/should've prevented it (so long as one's finger is off the trigger). Maybe hubby's finger was on the trigger when it let go? Glad no one got hurt.

 

[BP44]

I will bet money MrBorland is correct.
A range trip a few years back a good friend of mine did this and had it discharge(trigger still under tension) at a 45* angle down range. He is not a revolver guy and I fear that incident only made his case against them stronger.

 

[MrBorland]

Here are some pics of the innards showing how a S&W can sometimes get into a faux half-cock. As you can see, tolerances are plenty tight, so getting into the half-cock is easier on some guns than others. Note, though, that S&Ws aren't designed to half-cock, and so getting one there is neither safe, nor good for the gun.

Figure 2 shows the gun at full cock. The trigger nose rests against the (tiny) SA sear. To lower the hammer (figure 3), the hammer is held back, the trigger pulled, the hammer lowered slightly, and the trigger allowed to return fully. However, if the hammer is lowered while the trigger is held somewhere in the middle, the gun can jam (faux half-cock) when the trigger nose gets bound up behind the DA sear (figure 4). One can also achieve a faux half-cock if you manage to rest the trigger cam on the SA sear (figure 5).

Bottom line: Don't keep the trigger somewhere between fully back and fully forward when lowering the hammer. Not only should your finger not be on the trigger while lowering the hammer, you can manage to jam the gun.





Faux Half Cock:

 

[forindooruseonly]

Good info, MrBorland. I've known about faux-half-cocks and how to avoid them, but never really had them explained to me, or seen what happens with the action when it occurs. Thanks for posting those pics and explanation.

 

[Guillermo]

as Mr. Boreland said...it could not have gone off if the trigger were not back