Misfires on a 396 NG

[jem102]

I bought a 396 NG when they first came out and had ignition issues with it right from the start. It would fire "most" of the time with the Hornady 180 HP factory load but was very inconsistent with any other brand. As I have other guns it just sat for years and I carried my 1911 and Glocks. Lately I have gotten interested in wheel guns again and thought I would get this out and try to diagnose the misfires.
I stripped it down tonight and in the process of removing the firing pin to get some measurements I dropped it on the carpet. I have one of those magnets affixed to a long handle that I use to find lost parts and normally its quite effective but not tonight. So down on my hands and knees, which ain't easy at 71, and I locate the pin. Thinking this to be strange I held it to the magnet and zero attraction which surprised me greatly. Anyone know what their made of? My only guess is an exotic like Beryllium...
Anyway the pin measures .484 overall which I understand to be a little short and please correct me if I am wrong.
I ordered an extra length pin from Cylinder & Slide and was wondering if there are any special concerns, installation or usage tips involved.
The strain screw was tight when i Removed it. From the underside to the tip it measures .335 and .476 overall. I purchased this revolver new in the box from a dealer but it is obvious the screw has been dressed on the tip and I assume at the factory.
All comments greatly appreciated and thank you for reading along.

 

[steelslaver]

It could be a short firing pin, but, how much head space or rear gauge do you have? Also how much end shake. Excess gauge makes lets primer be farther away, end shake can use up energy from firing pin as cylinder moves forward. What do your misfire primers look like?

 

[armorer951]

Hope you get the problem sorted out. I believe the firing pin you have is titanium alloy.

Reference the longer firing pin, Cylinder and Slide recommends that if you dry fire to be sure to use snap caps. Personally, I can't recommend that particular brand, as I have seen two of them break over the last 3-4 years.

 

[jem102]

Thanks for the comments and advice.


No noticeable end shake but I will get the feeler gauges out and see what it is on head space. the firing pin dimple is light. i will try to get some pics up.


I went with C&S as I have had good experience with them in the past on other items. Would you care to recommend a brand please?

 

[armorer951]

I have been using the extended firing pins made by Power Custom. They are .510" long. I believe Apex still makes them also. Remember though, as always, any part can break. What I'm saying is that the Power Custom parts are not infallible. Also, hold on to your old pin.

When you install the new firing pin, make sure to check the firing pin cavity in the frame for dirt or debris, and clean it thoroughly with alcohol or acetone. Q-tips work great for this, but make sure you check for any stray cotton fibers left behind after cleaning and before the install. Leave the frame cavity, spring, and firing pin dry, as no lubricant is either required or desired.

 

[BLUEDOT37]

That factory firing pin is on the short-side.

Many of the new S&W firing pins I've bought recently measure in the .495-.498" range though.

I've used the C&S extended firing pins & have not had one break but be aware that in some revolvers that .510" length can be too much causing the FP to stick in the primer & not release quickly when cocking.

Also, my 396NG had tight throats, like many 696s had, & measured .4285" so I opened them up with a throating reamer as I mainly shoot jacketed bullets.

I hope you get that issues sorted out as the 396NG is an awesome revolver.

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[jem102]

Greatly appreciate all the information! This will get me on the path and I will report back on my progress.
What a great forum, where else could you get this much detail so willingly...

 

[steelslaver]

I do believe the frame mounted pins have more of a problem with length than hammer mounted. Fame mounted there could be some small variances in depth of hole, spring length, a bit of debris etc. As long as the firing pin clears the bushing and does not pierce the primers, I can only see a bit of extra length as a good thing.

I have a 296, a 396 and 2 325s and none off them have never failed to fire. As they are carry guns, other than removing the lock on them like every other lock gun I have, I will leave them stock as long as they never misfire.

 

[Doug M.]

My recollection is that S&W shorted firing pins in the past couple decades to comply with arbitrary standard that had nothing to do with any real safety issue. Sometimes the correct answer is a firing pin that is actually the right length. That sounds like what you are encountering.

 

[jem102]

My C&S firing pin arrived today and I am a little surprised at the dimensions and not sure how the C&S has more reach even though it measures .510 VS the .484 that came in the revolver. To the best I can measure the pin tip to stop shoulder id the same on both pins. The body section of the C&S is .0365 longer than the S&W pin but I am not understanding how that adds any reach to the pin. The glaring difference is the size of the window the retaining pin floats in. Apparently they decided the pin was being stopped by the retaining pin rather than the pin shoulder? Perhaps the extra body length allows the hammer to deliver more energy as the longer body section cannot escape the full force of the hammer? I don't know but please take a look and tell me what you think. Picture quality is not the greatest but it will show you what I am talking about. Thanks for reading along.

 

[armorer951]

Opinion....for what it's worth:

The added OAL of the pin and the extra length of it's cutaway allow for a longer protrusion through the breechface. The difference between the protrusion of my original OEM pin on my 640-1 and the new Power Custom extra length pin is approx .015". (hammer at rest, fully in battery)

Also, the additional space in the cutaway allows for more movement of the firing pin forward and back....or less restriction forward and back in the cavity. This extra cutaway space allows for the pin to sit in the frame with a bit more of the pin exposed to the hammer also.....or more protrusion at the rear too.

I believe the length of the tip in front of the shoulder of the pin simply serves to accommodate the spring.

 

[jem102]

Did some more measuring tonight and I agree with armorer951 that the larger cut out is what makes the difference.

The tip to shoulder is the same for both pins but the factory pin is stopped in its forward travel by the retaining pin in the much narrower window of the factory pin. The window on the C&S pin allows it to travel forward unimpeded.
I believe this is why I have heard the recommendation to use snap caps as I believe the intention is to have the primer as a forward stop. If the cylinder/chamber is empty the pin will batter on the forward shoulder in the firing pin boss which may become an issue over time and snap caps will prevent this.

The pistol is stripped down so I installed both pins with spring in place, set the hammer in and applied enough pressure to be sure it was all the way forward against the frame boss. By my measurements I got .04700 protrusion on the C&S pin VS .03125 on the S&W pin for +.01600 on the C&S.

The extra body length really is only to allow the longer window in the pin for more travel fore and aft of the retaining pin. As I see it that is where the added protrusion comes from.

After going through all of this it may be possible to gain .01000 just by filing the back of the window on the stock pin...
Brownells finally has factory firing pins back in stock and I ordered a couple just to check them out. My 396 was manufactured in 2008 and it will be interesting to compare them. If there is an obvious change I will try on of those as well.

Hope all this makes some sense and all thoughts appreciated.

 

[armorer951]

The other desirable thing about the use of snap caps is that they reduce battering of the firing pin spring during dry firing.

The use of snap caps not only helps the firing pin spring last longer, but also helps reduce collateral damage to the spring and pin while they are at work inside the frame cavity by dampening the pin's movement forward in the same way the pin is "restricted" during live firing.

 

[BLUEDOT37]

These pictures show a "best case" situation of their reach using a S&W factory firing pin (top) & an Apex extended firing pin (bottom) in my 325TR.

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[steelslaver]

I never worried about dry firing S&W centerfire revolvers until I got some alloy ones with frame mounted pins. That horrible click you get and knowing it is all being stopped by the pin shoulders when the pin is slammed forward says to me this can't be good on the either the spring, the firing pin, the cross pin, or the end of hole in frame or a combination of several or all.

 

[jem102]

armorer951 and steelslaver, absolutely agree that the alloy frames, firing pin and spring need protection from battering. At the least load the cylinder with 1X fired which should be good for a cycle or two.


BLUEDOT37, That is what I saw when I tested each spring. Wish I had been smart enough to put a case in the chamber to gauge it by as you did in your pics but just looking I don't believe my factory pin has as much protrusion as yours does. Are you still using the Apex in the pistol and how is it working?


Another question if I may. I purchased this pistol new in the box from a well known dealer in the area so have no reason to believe it is anything other but while cleaning up all the parts last night I noticed the strain screw has had the end dressed. Overall is .476 and tip to underside of the head is .345. Would the factory ever adjust the strain screw and do these dimensions seem correct?


Hope I am not being a pain but still new to S&W's learning as I go. All information appreciated.
Thank you!

 

[armorer951]

The reason it looks "longer" in the photo, is that Bluedot didn't use the hammer to push the pin forward in this illustration, he used a pushpin, which allowed the firing pin to go in just a bit deeper, to the shoulder on the firing pin, and below the frame hammer impact stop.

This very clearly illustrates the value and importance concerning the use of snap caps or empty casings, particularly in the aluminum frame revolvers. When used during dry firing, these devices prevent the firing pin shoulder from battering the frame, the firing pin spring, and "cushion" the impact of the firing pin itself.

 

[BLUEDOT37]

Are you still using the Apex in the pistol and how is it working?
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the strain screw... Overall is .476 and tip to underside of the head is .345. ...do these dimensions seem correct?

I still have the extended Apex firing pins installed. No problems with them.

I quit buying them for a few years & went to C&S after Apex changed the shape of the nose from rounded to pointed, which I don't prefer. They eventually changed back though.

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The strain screws, of that style, that I've documented their dimensions on run ~.46x" / .33x" so yours are on the generous side by comparison. The later length, of the threaded portion, is the one that matters.

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[jem102]

Gentleman, I greatly appreciate all the information!!!


BLUEDOT37, outstanding detail, makes it very clear. As best as I can measure the notch on the C&S is .160 as well. The tip does have a radius but not as well blended as the Apex.
The length on the strain screw makes me think the factory did dress it down some.


Again to everyone thanks so much for sharing your knowledge...