DA misfires

[chriske]

I recently bought a used S&W mod 14 .38 spl. revolver .
It is a beauty, in excellent condition,well cared for & the price was ever so right.
The first time I tried it out at the range, it proved pleasant to shoot and accurate
beyond my expectations ..... in single action.
As soon as I tried to shoot it DA-wise (which I prefer) it failed to fire 2 times out of 6.
This happened with different sorts of ammo (factory as well as reloads, and the
reloads with different kinds of primers), and could not be traced to one or two
specific cylinder chambers.
Close examination revealed something I think weird: i never saw it on any S&W revolver ever before. The portion of the frame through which the hammer passes shows a sort of
tiny through worn out on its top. Could it be the firing pin gouged that out and/or is hitting
the frame occasionally ? Why would this cause" misfires in DA and not in SA mode ?
What can be done about it ?

 

[Brasso]

It probably needs a trip back to S&W. However, there is one thing you can look at. Make sure the tension screw is tight. This is the screw at the bottom front of the grip frame. If it backs out it can cause light strikes. Make sure it's tightened all the way. Other than that, it will need the care of a gunsmith.

 

[SDC]

It sounds like this was a revolver "tuned" for bullseye; did you try Federal primers in it? More than likely, the strain screw at the front of the grip has also been backed off to the absolute minimum, to give the lightest possible trigger pull.

 

[Phil DeGraves]

+1 on the tension screw. This is the most common cause of light strikes. If that doesn't work, you can try to replace the mainspring. It is an easy job that does not require a smith and the spring kits are available from Brownells for about 15 dollars.

 

[chriske]

Thanks for the swift response.
As to the tension screw: I can't get it any tighter.
I'll try another mainspring, probably switch one out of another K-frame S&W I own (mod. 15 - should work, no ?)
As to the possibly necessary trip back to S&W : I still remember when the firing pin from my -then new- mod. 63 broke, that kind of trip took 9 months.
I guess Belgium IS far, far away.

 

[MrBorland]

Wouldn't a loose tension screw affect single action reliability as well? I was thinking something more specific to the DA trigger mechanism, such as mis-adjusted DA sear letout, in which case the the DA trigger may be breaking a wee bit too early.

 

[chriske]

MrBorland, sir, that makes sense .
But wouldn't correcting a mis-adjusted DA letoff involve some
highly specialized gunsmithing ?
Or could this be remedied by replacing the whole trigger (or hammer ?)

 

[SDC]

Yes and no; the hammer falls a further distance in SA than it does in DA, and that extra travel gives it a little more "oomph" when it finally strikes the primer.

 

[Old Fuff]

The most common causes for double-action misfires are:

1. The mainspring strain screw has been backed out or shortened in an unwise attempt to lighten the trigger pull – either single-action, double-action, or both. The solution is to replace the screw, which is not expensive.

2. The mainspring itself has been altered, or replaced with a lighter one. The solution is to replace the spring with a factory stock one. No gunsmithing is required, and the spring is not expensive.

3. The cylinder has developed end shake (back and forth movement, rather then rotational). Correction is not difficult, but does require the services of an experienced gunsmith.

Having the hammer or trigger rub the frame on one side or the other is not unusual. This condition may be corrected by placing a washer or “bearing” on the hammer stud (the pin the hammer rotates on) between the hammer and frame. This very thin bearing will shift the hammer slightly to the left or right, as needed. The bearings are available from Brownells (www.brownells.com) and are not expensive. The services of a gunsmith may or may not be necessary, depending on the experience and knowledge of the gun owner.

Brownells also sell a shop manual (The Smith & Wesson Revolver – A Shop Manual by Jerry Kuhnhausen). This book is extremely useful for anyone that needs to fully understand the workings of a pre-MIM lockwork S&W revolver, or one who may have to service their own guns where warrantee service is not available.

 

[MrBorland]

Lots of good info here. If none of these pan out, I'll throw one more out there, but first have to ask - are the grips original? After market rubber? Some claim that overtightening of the grips screws on rubber grips can pinch the mainspring and lead to ignition trouble. Never seen it myself, but it makes sense, and it's by far the easiest fix, so I thought I'd mention it.

 

[chriske]

Thanks, all !
I already have several things to try out . Most (substituting parts) involve some tinkering at home-trip tot the range-more tinkering at home, so will
take some time to report on.
But you've all been so helpful I definitely will let you know what, if anything, worked.

This is a great forum & you're fine people.

 

[chriske]

S&W DA misfires cont'd & question

I promised to follow up on my S&W-14 DA misfires.
Here's what I tried so far to no avail :
- tightening tension screw (was already as tight as possible)
- swapping tension screw from S&W mod 15
- substituting main spring : once with WILSON's aftermarket spring, once with S&W mod 15 factory spring

After having removed the side plate I noticed some kind of "shelf" on the inside (just forward of the locating pin on top & in front of the sliding hammer block thingy.) , possibly the hammer hit the inside of the side plate & "threw" that ridge/shelf "up". I polished that away as carefully as I could. Coincidence, pure luck or Eureka, anyway, number of DA failure to fire dropped.
I think this IS a problem of hammer-hititing-frame order.
That's why I am extremely reluctant to substitute the hammer with the mod 15's still perfect one, for fear of damaging it as well & wind up with 2 non-firing guns.
Either the hammer/firingpin assembly is mismatched or maybe the stud on which the hammer pivots is out of whack, as someone suggested.
I think I'll take it to a 'smith.
Thanks to all for the help & suggestions.

B.T.W. on some S&W revolvers with hammer mounted firing pins, it is spring-loaded. On others it isn't. Why is that, what does that spring
achieve (or prevent) & which system is best in terms of longevity & reliability ?

 

[Old Fuff]

B.T.W. on some S&W revolvers with hammer mounted firing pins, it is spring-loaded. On others it isn't. Why is that, what does that spring
achieve (or prevent) & which system is best in terms of longevity & reliability ?

The purpose of the spring is to better center the hammer nose (firing pin) in the hole it passes through in the frame. If a hammer doesn't have one it was made before the spring was introduced. They are not necessary, but nice. In most cases if you have an older hammer the new hammer nose and spring can be installed in place of the original one.

 

[chriske]

Thank you for the information, Mr Fuff !
According to the sticky on this forum my mod 14 was probably made around
1968.
At first -amateuristic- glance, this hammer nose spring seems useful.
If any hammer/firing pin work should appear necessary on my gun, I'm inclined to ask the gunsmith to incorporate it. But if "it ain't broke", I will not insist on "fixing it".
Thanks again !

 

[Old Fuff]

Watch the firing pin and breech face for signs of battering - which is unlikely.

Smith & Wesson's K-frame revolvers were introduced in 1899, and the design was pretty well developed by 1905. Thereafter few meaningful changes were made. Consequently, unlike some other designs, it's well de-bugged, and has been for decades. I don't fix anything that doesn't need fixing either.

 

[Round Gun Shooter]

All good info here. As for the marks on the frame, I would guess someone was trying the action with the side plate off and pulled the trigger.