HELP! Firing Pin Misses Primer

Bahamaroot · Nov 2, 2015

I have a 19-4 ser# 39kxxxx.

When shooting in double action the firing pin sometimes completely misses the primer. I've had it miss as many as 3 of 6 shells. In single action it does just fine.

I have noticed that the firing pin has some play to it on the hammer. In lock up the timing looks perfect but I'm not a smith either.

I bought the gun about 10yrs ago from a retired army vet neighbor that was moving to a retirement community. He guessed the gun had less than 1k rounds through it and hadn't been shot in probably 20yrs. I have only put about 500 rounds through it. It has been over the last 150 or so that it has really started acting up. It locked up tight a few times but hasn't done that for a long time. The "missing the primer" in double action is it's real hang up right now!

I'm not well versed on these mechanically but any ideas?
Thought I'd run it by you guys first but am ready to send it off to S&W for evaluation, or should I just visit someone locally?

Thanks!

bigggbbruce · Nov 2, 2015

Misses the primer..?? Or is it a light strike with no ignition.

Strain screw coming loose?

Hapworth · Nov 2, 2015

Sounds like it might be a carry up issue; could be from hand/extractor tooth engagement, possibly from the double-action sear shortened too much.

What happens in slow double-action dry fire? Does the hammer drop before or after the cylinder stop engages?

Hapworth · Nov 2, 2015

bigggbbruce said:
Misses the primer..?? Or is it a light strike with no ignition...

That's a good question and important distinction...

reddog81 · Nov 2, 2015

I'd bet that it's a loose strain screw causing light strikes. The timing should not be off with so few rounds through the gun.

If the gun is actually striking the brass or hitting the cylinder and completely missing the primer than do not shoot until you have a gunsmith inspect the gun.

Bahamaroot · Nov 2, 2015

The cylinder stop engages before the hammer drops.
The strain screw is very tight.
The pin totally misses the primer and leaves a light mark on the brass next to the primer.

Bahamaroot · Nov 2, 2015

And remember this is random and only in double action. Sometimes it will strike fine, sometimes it will miss completely but I can no longer shoot a full cylinder without at least one full miss.

Hapworth · Nov 2, 2015

Bahamaroot said:
...The pin totally misses the primer and leaves a light mark on the brass next to the primer.

To the left, right, or both?

Bahamaroot · Nov 2, 2015

Thinking right mostly if not always. Really was too dumbfounded to take strong mental note.

dfariswheel · Nov 2, 2015

To help simplify diagnosing the problem, this is probably one of two things that can happen in double action, seldom in single action:

1. Failure to "carry up".
This is a situation where the gun is out of time and the hammer is dropping before the cylinder is locked, which allows the firing pin to strike off-center.
This is not too common because usually when the trigger is pulled in DA the inertia of the cylinder pushes it all the way to locked.
This is usually caused by an action out of adjustment.

2. Cylinder "throw-by".
This is a situation where something is causing the cylinder locking bolt to not catch and engage the cylinder locking notch.
Result is the cylinder rotates too FAR and by-passes the chamber slightly.
Result is again, an off-center firing pin strike.
This can be caused by a weak or fouled bolt spring or an action gummed up with fouling and old lubricant.

To help figure out what's going on, load the cylinder and use a marker to make a mark at the 12:00 o'clock location of each case in the chambers.
Then after firing the gun carefully open the cylinder and check to see which side the off-center strikes are on.
In the S&W, strikes to the left side at around 11:00 o'clock are failures to carry up. (Cylinder didn't turn far enough).
Strikes to the right side at around 1:00 o'clock are cylinder throw-by. (Cylinder turned too far).

Once you know which it is, possibly we can help diagnose the cause.

S&W and Colt hammer mounted center fire firing pins MUST have some free up and down movement. This is to allow the firing pin to align itself with the firing pin hole in the frame.
They should have minimal side to side movement.

John R · Nov 2, 2015

Possibly a broken hammer stud.

planojack · Nov 2, 2015

Have you checked for any old powder grains, etc., in the frame that does not let the frame quite lock up tight?

jag312 · Nov 2, 2015

When was the last time it was disassembled for a thorough cleaning? If it hasn't been thoroughly cleaned in 30 years, it needs it. Dirty guns with old oxidized oil don't work too well.

Bahamaroot · Nov 3, 2015

jag312 said:
When was the last time it was disassembled for a thorough cleaning? If it hasn't been thoroughly cleaned in 30 years, it needs it. Dirty guns with old oxidized oil don't work too well.

Oh it's been far to long that's for sure. Not being shot much it has seen very little cleaning and I haven't broke it down for a thorough since I first bought it.
After I started this tread the idea of it being gummed upped or something started to swirl in my head if that might be a contributing factor.
Not sure when I'll have a chance to shoot it again but it will be thoroughly cleaned first and more specific details taken note of. If it is still a persistent problem after the cleaning I guess I'll seek out a local smith or it will be off to S&W and let them work it out...$$$...

Bahamaroot · Nov 3, 2015

And thanks everyone for the ideas and things to look for, I hope to get this worked out. This is a sweet revolver when it isn't acting up!

shootn99 · Nov 3, 2015

A quick way to check for proper carry-up is to use your thumb to slowly pull back the hammer and listen for the locking bolt to engage the cylinder. If it does not engage before the hammer locks back, the weapon is out of time and needs some gun smith work before being used again.

bigggbbruce · Nov 3, 2015

shootn99 said:
A quick way to check for proper carry-up is to use your thumb to slowly pull back the hammer and listen for the locking bolt to engage the cylinder.

Not exactly.. the cylinder stop locks into the cylinder.. The locking bolt engages the extractor rod to keep the yoke closed.

old&slow · Nov 3, 2015

I had a similar problem with my S&W 610. I sent it back to the factory and they said they replaced the cylinder stop. Had it back in a few weeks. It has been working fine ever since..

Bahamaroot · Nov 5, 2015

Broke it down and gave it a thorough cleaning, everything looks ok. Hope to get a chance to shoot it one more time next week but I have a feeling this ones going back to Smith.

Thank you everyone for thoughts on this, your teaching me more all the time!

andyo5 · Nov 5, 2015

The firing pin can only strike the primer through a small aperture in the firewall. It can't move sideways and strike the brass.
Ergo...it must be the round moving sideways and not the firing pin.
Sounds like the cylinder is able to wobble a bit in double action. Or else it is not completely locked into position by the bolt.

HELP! Firing Pin Misses Primer

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