S&W New Departure Firing Pin Sticking

[Johnm1]

Here is the pistol:



The issue is sometimes the firing pin protrudes from the recoil shield after the hammer comes forward. It can take significant force to 'push' it back in. As in sometimes I can't push it back in with my finger as it hurts too much and it takes a blow with a plastic hammer. Sometimes it gets 'wedged' pretty good.

Here are the parts involved:


I have been successful in removing the firing pin bushing. The spring was a little weak and I made a new one with a little more 'force'. Here are some detailed pictures of the actual pieces from the actual pistol:





As you can see, the firing pin has a bevel on the bottom. I'm surmising that the bevel is catching on the inside edge of the bushing as the bushing necks down to the diameter of the firing pin. Here is a close up of the bevel on the firing pin.



About halfway up the bevel you can see some deformations that I think is the point where the firing pin 'wedges' into the bushing.

Now there was one other observation. I chucked up the firing pin into the drill and there was a slight bend in it. That too could cause the bind/wedge. I did tap it lightly and lo and behold it did straighten almost straight.

I have polished every surface on both the firing pin and the bushing with polishing compound in the hopes it would be 'slippery' enough to not catch/wedge. I very lightly used a tapered round file to try to soften the edges inside the bushing where the tapered part of the firing pin contacts the bushing.

I'm open for suggestions. Although the polishing/straightening did improve the situation, it does still bind/wedge sometimes though not as hard as before the polishing. The parts have close to 130 years of wear on them, so I don't think there is any circumstance where filing or sanding will improve the problem. Note that even though there is 130 years of wear on the parts, the tip of the firing pin looks to be in the same shape as the day it was manufacturered.

 

[Col. Harrumph]

Are you sure the hammer is rebounding? Stripping the innards and giving it a good clean & lube would usually be step one for any gun in any situation. (Although it looks like you're there already.) BTW I know how hard it is to give up on a part original to the gun, but gunpartscorp,com has replacements for the f.p. (but not the spring or bushing).

 

[Johnm1]

Are you sure the hammer is rebounding? Stripping the innards and giving it a good clean & lube would usually be step one for any gun in any situation. (Although it looks like you're there already.) BTW I know how hard it is to give up on a part original to the gun, but gunpartscorp,com has replacements for the f.p. (but not the spring or bushing).

Yes, I am certain the hammer is rebounding. In this operation I learned that the hammer rebound is a result of the geometry and the tension on the mainspring. I learned that if the tension was incorrect on the mainspring the hammer would bind on the mainspring stirrup. As it turns out, the mainspring and the hammer and the stirrup are all designed so that the mainspring reaches the at rest position prior to hitting hammer. It is only the weight and the momentum of the hammer that allows the hammer to strike the firing pin. After that the hammer returns to its at rest position. I am putting together another post on that geometry and the engineering involved in accomplishing it.

I never considered replacing any of the parts. I'm not sure why that didn't come to mind. As it turns out Jack First has all three parts new. That may be the wisest course of action. I have no qualms about replacing original parts. The way I look at it, a repair made today could have been made 75 years ago. I'm not sure I'll go that way though. The polishing I've done has reduced the issue to intermittent at best. I'd still be interested to hear what others have to say even though I may well buy a new firing pin/bushing.

 

[a5werkes]

From the peanut gallery. My Rule is always first modify the least expensive or most readily available part. I can see the bend of the firing pin shaft at its extension from the bevel. I would take a few thousandths off the surface of the firing pin shaft & bevel and /or open up the bushing aperture a few thousandths; the combination of increasing tolerances might prevent the post-firing binding issue.

 

[Johnm1]

From the peanut gallery. My Rule is always first modify the least expensive or most readily available part. I can see the bend of the firing pin shaft at its extension from the bevel. I would take a few thousandths off the surface of the firing pin shaft & bevel and /or open up the bushing aperture a few thousandths; the combination of increasing tolerances might prevent the post-firing binding issue.

The peanut gallery is who I asked the question to! It's not like there is a S&W tech who works on these things around reading this post.

Agreed on the least expensive/most readily available part. And the firing pin is available.

The pictures were taken before I straightened the firing pin. It isn't absolutely straight now but it is straighter than in the picture. I was surprised at how little force it took to straighten.

I considered taking some material off of the firing pin at the bevel and where it wasn't straight. But my gut tells me that removing material is very often the wrong decision. The part worked when it was made and 130 years of wear didn't add material to the part. So removing material, though it may help the specific problem, will often weaken the part to the point of breaking or sometimes cause new problems that we didn't think of. In this case we are talking about a couple of thousandths and it probably wouldn't pose a threat. But the concept is real.

I could bevel the inside of the bushing a bit more but the 'tunnel' the firing pin passes through has a length to it and I wouldn't be able to increase the inside diameter for that length without a properly sized drill bit. Plus, I'm pretty sure that the straight length that the firing pin passes through helps keep the firing pin straight.

The more I think about it the more I think the problem came about due to the bent firing pin. FYI - at one point the firing pin protruded far enough out of the recoil shield to prevent the revolver from being opened and it is probably the 'interference' between the protruding firing pin and the ratches on the back of the cylinder that cause the bent firing pin recently.

 

[Jackrabbit1957]

Hi Johnm1, could the spring be binding up the firing pin? Was looking at the pics and that thought occurred to me. Another idea would be to color the firing pin with a sharpie marker and see where it's marking the pin. Removing the shiny spots slowly should free things up.

 

[PRD1]

The firing pin you show is certainly a replacement. I have made several new ones for the 'Lemon Squeezer' Smiths, and no taper is needed on the forward part of the pin. It also appears that the pin is made of too-soft material. I'd suggest that you make a new one of suitable steel - Brownell's sells an assortment of steel rod called 'Stressproof', IIRC, and that has proved to work well. The forward section of the pin should not be longer than needed for good ignition, and the rear (behind the flange) should not permit the hammer to contact it while at rest.

PRD1 - mhb - MIke

 

[Ethan Verity]

This is interesting, I had the same exact problem with my Ruger Redhawk 44 Magnum. The firing pin in that gun looks awfully similar as well! I ended up reaming out the bushing to open it up very slightly so that it would no longer catch on the firing pin bevel, which resolved the problem.

 

[Johnm1]

Hi Johnm1, could the spring be binding up the firing pin? Was looking at the pics and that thought occurred to me. Another idea would be to color the firing pin with a sharpie marker and see where it's marking the pin. Removing the shiny spots slowly should free things up.

I considered that the spring might be part of if not the problem. I also considered smoking the pin to see where it was binding, but installation of the pin and bushing isn't a clean/easy operation and I doubted that iI could determine where it was binding compared to where it rubbed during installation. @PRD1 s post below is an interesting view of the condition.

The firing pin you show is certainly a replacement. I have made several new ones for the 'Lemon Squeezer' Smiths, and no taper is needed on the forward part of the pin. It also appears that the pin is made of too-soft material. I'd suggest that you make a new one of suitable steel - Brownell's sells an assortment of steel rod called 'Stressproof', IIRC, and that has proved to work well. The forward section of the pin should not be longer than needed for good ignition, and the rear (behind the flange) should not permit the hammer to contact it while at rest.


PRD1 - mhb - MIke

That is interesting. I had assumed that the taper was put there for a reason. But maybe not. I had assumed that thepart of the pin that contacts the primer had not been battered and was pretty hard. Mostly because it appears that the very tip is machined to a slightly smaller diameter than the overall length of the pin. But what do I know.

This is interesting, I had the same exact problem with my Ruger Redhawk 44 Magnum. The firing pin in that gun looks awfully similar as well! I ended up reaming out the bushing to open it up very slightly so that it would no longer catch on the firing pin bevel, which resolved the problem.

The best part of forums like this is that we can share ideas that can cross over to different platforms.

I ordered a replacement firing pin and spring from Jack First and it arrived though I haven't unpackaged it yet. I did not order a new bushing. Its cost was a little up there and to the best of my knowledge it isn't the probme. A new bushing would also introduce a fitting operation that has very close tolerances I wasn't looking forward to. I hope I don't regret that decision. I have another order in the works with Jack First and I'll add the bushing if the new pin doesn't solve the problem.

I'll report back on the shape of the replacement firing pin I received from Jack First but it looks like they put a taper on it as well.

 

[Ethan Verity]

In follow up to my previous post, here is a picture of the firing pin from a Ruger Redhawk to show how very similar they are. It's neat how this resulted in the same exact problem, on two completely different guns from very different eras. Perhaps gun manufacturers/designers should take note!

 

[Jackrabbit1957]

I kinda wonder about that taper, it looks like a morse taper to me, if so it might be wanting to lock together with the bushing if it has a corresponding female taper, might be worthwhile to flatten out the taper and see what happens.

 

[4v50 Gary]

LIghtly polish the FP. All those burrs can result in it hanging up. No file, just emery paper.

 

[Johnm1]

LIghtly polish the FP. All those burrs can result in it hanging up. No file, just emery paper.

Your point is well taken. I have polished using 600 grit sandpaper. So it looks better than the pictures above. I really think the issue is the bent part. I was able to straighten it a bit but I think that is the real problem. I'm going to replace it with the one I got from Jack First. BTW - it looks the same as the one that is currently in the gun with the taper in it. Minus the burrs and dents of course.

I'll be able to work on this one this weekend.

Thanks.

 

[Johnm1]

The replacement firing pin and spring seems to have solved the issue. I'm pretty sure that @4v50 Gary 's advice to polish the pin would have also worked. The spring that Jack First sent was significantly stronger than the original or the replacement I made. So it too might have corrected the issue.

Some minor fitting/polishing of the 'barrel' of the new pin was required on the new pin to assure smooth movement of the pin. Firing pin projection of the new pin/spring was noticeably less but I'm pretty sure it is enough. I'll have to prime some empty brass to do a final function test. As a double action only it is not easy to measure the projection even if I disable mainspring.

 

[Johnm1]

Functioned perfect.