Hello,

have these strange corresponding marks on cylinder and frame. On the cylinder they are fife times. Looks as if cylinder gets into contact with frame on shooting. Inspecting the gun I can't verify this. Cylinder is clear of frame, no excessive play to be seen. Looks as if Cylinder can't get into touch with frame at this position.

sc340Cyl.jpg

Thanks for your help.
Fritz

Only thing I can think of is something got stuck there and scratched it. Maybe somebody tried to bend the yoke around and stuck a wedge in it at that point.
The gun can't make that mark by it's self.

__________________
NRA Benefactor Member

If you have that same mark in five locations on the cylinder (near the stop notches), something's seriously wrong. I'd phone S&W and have them send a shipping label, so they can check out the gun (no charge to you). I wouldn't shoot it as is.

How about posting a photo of the recoil shield and the back of the cylinder. Maybe check the frame under the barrel for a crack.

__________________
"I also cook."

Beats me. Is it just on the surface, or does it dig into the metal?

__________________
NRA Life Member

The cylinder shouldn't touch the frame there..
I too would be thinking the yolk, which is aluminum alloy BTW on the Airlites, may be misaligned or bent slightly..
I would be calling S&W for the shipping label..
If you carry this piece for Self Protection nothing is too good for it..
Let us know if the cylinder touches on each cylinder bolt stop & any other things that look amis..
Keep us informed of what S&W does for you on this matter..
GOOD LUCK!
Gary/Hk

__________________
MightShowYouHisSmith&Wesson

Here are some more pictures:
Bridge.jpg
Cone.jpg
Gap.jpg
Frame and cylinder are clear from each other. But when I force the cylinder down with my fingers, I nearly - but not totaly - can close the gap. I can imagine that the force of a 357 load will be able to force this completely down.
recoilShield.jpg
leftSide1.jpg

Thanks for your input,
Fritz

yoke.jpg
Fritz

Did look at the gun again. For ease of understanding I reference the explode at
SW36

Between the Locking Bolt (5147) and the Center Pin (7062) there is quite a bit of play say 90% of what is needed to unlock the cylinder. The Center Pin Spring (5227) is not very strong. I easily can imagine that under the heavy recoil of a 357 magnum load in this 12oz gun the Center Pin (7062) moves forward against the somewhat weak Center Pin Spring (5227), gaining momentum and pushing the Locking Bolt (5147) that little bit that is lacking to unlock the cylinder forward.

If I push the Center Pin (7062) forward using the Thumbpiece (5613) I easily can get the cylinder in touch with the frame.

Guess that is the catch. Can anyone owning a Scandium Snubby confirm that this is NOT the case with his gun.

BTW, as the tip of the Center Pin (7062) facing the Locking Bolt (5147) looks "worked" on my gun, can anyone tell me how deep the Center Pin (7062) is in the Extractor Rod (5255)? Maybe that someone messed around with that piece because the cylinder was somewhat difficult to close. I am wild guessing ;-)

Thanks,
Fritz

The more and more I think about it, I come to the believe that it is the Center Pin and Lock Bolt which are the culprits.

On maximal protrusion the Center Pin barely touches the Lock Bolt. You nearly can't tell that the both parts are touching each other on unlocking and locking the cylinder. Eyballed about 3 thousands overlapping of the two parts.
maxProtrusion.jpg
The Center Pin recesses into the Extractor Guide about 6 to 7 hundreds of an inch. Center Pin looks as if it has been filed down and shows big marks.
Recess.jpg
Just to be complete a photo of the Lock Bolt:
LockBolt.jpg

Another wild guess:
The initialy rough MIM parts of the Thumb Piece and the opening mechanism lead a customer to return the gun for repair. The gunsmith tried to fix the problem in taking some resistance on the closing by simply filing down the Center Pin. Did not work, customer returned the gun, was refunded and the gunsmith looked for another customer. That is the moment when I enter the picture ;-)

What do you think about that? Can anybody owning a J-Frame compare his gun to mine?

Thanks,
Fritz

The locking bolt should engage the extractor rod. It should be in contact with the center pin. Clearance between the center pin and the locking bolt gives the center pin a "run" at the locking bolt under recoil. When you push the cyl release (and bolt) forward to release the cylinder the bolt should be flush with the face of the recoil shield and the center pin should be flush (or extend minimally beyond) the end of the extractor rod.

Is the locking bolt (in the barrel underlug) butchered or stuck so it doesn't extend properly and engage the extractor rod? The spring preload on the locking bolt helps the center pin stay put under recoil (along with the center pin spring). Has the end of the center pin been shortened (butchered) on the end that engages the recoil shield? Has the center pin spring been clipped/shortened?

The locking bolt does virtually not engage in the extractor rod. It only goes about 3 thousands into the extractor rod. You can get an idea of this if you look at my post from 8:13am. Not sure, but the locking bolt has working marks on it. Might be "butchered". It is not stuck anyway, it moves freely, but is in any case to short to engage into the extractor rod.

The center pin looks as if it has been "butchered" at the end facing the locking bolt.

At the site facing the recoil shield, the center pin has a "factory" look, i.e. no marks of filing or so.

The bolt that is manipulated with the thumb piece is flush with the surface of the recoil shield when I put the thumb piece fully forward. This looks good.

tomcatt51 it looks as if you are right. The center pin has about 6 to 7 hundreds room to run and gain momentum to push the locking bolt about 3 thousands. Then the cylinder is unlocked at both ends.

Trying to understand what is going on,
Fritz

Just another oddity. Cylinder gap is about 2 thousands. Somewhat tight, isnt it? And the barrel facing the cylinder is not realy square. 2 thousands of cylinder gap on one side, 4 thousands on the other side.

The locking bolt definitely does not engage in the extractor rod more than 3 thousands. As the locking bolt is kind of a cone, the cylinder is not led by the locking bolt. Guess the locking bolt has been shortened to ease the operation of closing the cylinder.

A puzzeled Fritz

The uneven B/C gap is pretty common, if you look at the barrel face you can see the marks from the gap being "adjusted" with a file. You check B/C gap with the cylinder held to the rear, maximizing the gap.

Sounds like the locking bolt needs replaced for starters and maybe the center pin if it doesn't come up at least flush with the extractor rod. You're trying to keep the center pin from disengaging the recoil shield during recoil, which obviously is a bunch with a gun that light shooting .357 mags.

What about the stress the yoke and its bearing in the frame, hence the whole frame, has undergone during unlocked shooting? After all the yoke has been bent quite a bit and alloy isnt famous for benting. Usually it is said to crack before benting.

Should (and can) I on returning the gun insist on replaement of the stressed parts?

Fritz

Did send the gun back. Stay tuned, I will keep you informed about the repair.

Beforehand another question. The surface of the cylinder and the frame are "spoiled". The visual effects of the destroyed finish don't bother me at all. But are there any negativ effects to be feared, kind of starting point for oxidation or the like?

Is it necessary to replace the "bent" parts, i.e. crane and frame?

What should I require them to do?

Thanks for your opinions!
Fritz

Flexing and bending are two different things. It the yoke was "bent" there would be permanent mis-alignment vs "flex" which allows the cylinder to move (contact the frame) but return to it's original position.

Apparently the phenomenon is not completely new. See the post of user johnbffb in the thread linked below:
S&W 329PD cylinder lockup - Shooters Forum

Fritz, a man depreviated of his wheelgun

Found another one. Sold as new "exhibition gun", exposing the marks. Is there anybody out there, owning a scandium wheel gun with the marks? Would be interesting to learn about this.

How often the inertia of center pin and locking bolt overcome their corresponding springs force to unlock the cylinder when you shoot magnum loads from a scandium gun?

Fritz

Fritz,

My 340Sc has a mark adjacent to and just to the front of the cylinder stop. It is like a triangle pointing to the front of the frame. The base of the triangle is just slightly narrower than the cylinder stop opening's width. The length of the triangle is slightly less than the length of the cylinder stop opening's length. Basically, it looks like a little Christmas tree shape with it's wide portion adjacent to the opening.

There is also a square mark behind the opening, between the opening and the bottom of the recoil shield.

Now, 2 years ago I had a problem when cylinder wouldn't open on 2 chambers. I sent it to S&W and they "repaired the extractor rod". IIRC they said it was slightly bent. I don't know if the marks were there before or after this problem or were caused by it.

I wonder if it is possible that the alloy frame and titanium cylinder momentarily flex and contact each other during firing, especially if everything is not aligned correctly.

BTW, when the cylinder is closed and I push on the thumbpiece, the locking bolt protrudes out the front approx. 1/8" (just a guess on the measurement). When at rest it is just a slight bump sticking out.

The finish wear on the front of the cylinder is normal and AFAIK not a problem.

Good Luck.

__________________
NRA Life Member

perpster, thank you for your input. Are the locking bolt and the center pin in contact when the cylinder is closed? If there is a gap, how wide is it (eyeballed)?

My guess is that if you (me) don't fix the problem with the cylinder locking as indicated by these marks which I described in my initial posting you will end up with a bent cylinder axis or a ruined frame. If you don't get a serious problem caused by a bullet not properly entering the forcing cone...

Thanks again,
Fritz

The rearward tip of the locking bolt is slanted, so that the center pin can slide past it and lock in place. When closed up, the entire slanted tip of the bolt is inside the cup at forward end of the ejector rod. You can just barely make out the beginnings of the slanted cut-off portion. Also, when closed up and the thumbpiece is pushed all the way forward, the front tip of the center pin is visible extending past the forward edge of the ejector rod tip, and the locking pin gets pushed into the underlug/shroud so that the non-slanted portion just disappears, leaving only the slanted tip visible to the point where the center pin is making contact in the space between the underlug/shroud and the ejector rod tip.

Hope this helps.

__________________
NRA Life Member

My brand new 329pd,(14 rounds total), has marks on it like #2 & #4.

I found this on the internet sometime back. Convinced me to check my revolver and mine was cracked in the same location. S&W replaced the frame. Check out the link for photos.
The Gun Zone -- S&W Model 340PD

Hello,

in Germany, only certified gunsmiths are allowed to work on guns. So me, I would not be allowed to change the centerpin of this gun. The idea behind this is, that the gunsmiths are protected in order to do a job that good, that a customer is unable to estimate it. Old mediaval logic, has nothing to do with a modern view of citizenship. But that is the way the old world is ogranized like. The gunsmith are organized in medival groupings called "Zunft" and they determine who will become member of the club and hence can control competition. For the best of "the citizen", obviously.

Furthermore a government agency called the "Beschussamt" has to test every gun before it can be sold and after any repair is done on most stressed parts like cylinder and barrel. They fire the revolver with pressure 30% above the CIP (which is higher than SAAMI) with one round per bore in the cylinder. Afterwards they have to check the most stressed parts (like the cylinder) for any failures (what IMHO would cover the marks on my gun). They also have to check functionality, which includes wether the gun securely locks.

Thus I had to go back to the gunsmith to have him fix the gun. I wrote him, that the combination of short centerpin and somewhat week springs is the probable cause of the problem.

Now the gun is back with me. Gunsmith said he visually inspected the gun and could not detect any problem. And as the "Beschussamt" has tested the gun, he ruled out that there could be any anomaly. He refused to consider the marks. Nor did he any test to verify the problem. Not his business.

He offerd me to make the locking pin protrude a little more and to oil the gun - but insisted that he has no obligation to do whatsoever. He further added that it is impossible to shoot this gun with 357magnum loads due to recoil. He said it is evident that this gun is only to be shot in 38special. Only in case of defense you might fire one shot in 357magnum. Call me a fortune teller, I would not take offense, sounds really unbelievable.

I got the gun back, the locking pin protrudes about 3 thousands more than before. Still, when the cylinder is locked, the centerpin is this far recessed, that it is more than 4 hundreds (eyeballed) off the locking pin and thus still has quite a bit of room to gain momentum.

Had no chance to go to the range to check the gun, it's just to cold over here.

What I will do is the following: I will put a small piece of tape at the frame where the marks are and shoot with a very mild 38special load. Predicted outcome: Tape will not show any marks.

Then I will load factory ammo from Sellier&Bellot, 158grs conforming to CIP (above SAAMI). Predicted outcome: Tape will show marks.


If things are going like i predict, I will send the gun back again and ask him to change the centerpin.

If he refuses, I will contact the federal agency responsible for the surveillance of the gunsmiths. Again I dare to predict what will happen. As the same breed of men is sitting in the institutions controlling the "Zunft" and as in doubt only members of the "Zunft" (basically a face-to-face-group) are accepted to judge the case, this will only cost me my money and my time.

Felix Americas!

Fritz

This reads like a bad dream.

Hello,

finally it got warm over here, about 32°F. At least warm enough to got to the range ;-) So I have been there. Results as expected: The gun is not shootable.

I did cover the old mark on the frame with ink. Before shooting, it looked like that:
before.jpg

Then I shot a mild 38special load (Remingto 110gn SJHP before 3gn of Trailboss, my chrony reads about 670fps shot from my 6"Ruger for this load). After about 20 shot, it looked like that:
after38.jpg
Conclusion: When shot with 38special, no contact between frame an cylinder.

Next I shot a 357magnum factory CIP-conform load with 158gn from Sellier & Bellot.
357CIP.jpg

After only one shot the frame looked like that:
after357CIP.jpg

Conclusion: CIP-conform 357-loads are too hot for the gun.


Next test was a 357magnum factory SAAMI-conform load with 158gn from magtech. This time I emptied the whole cylinder before looking and getting this result:
after357SAAMI.jpg

Conclusion: SAAMI-conform 357-loads are too hot for the gun.

Next I shot a mild 357magnum handload (180gn Remington SJHP before 5.5gn of Titegroup, a min load according to hodgdon, thus well below SAAMI). Again the frame had contact with the cylinder.

Will bring it back to the gunsmith. He is one of the biggest in the country and after all has to loose some reputation. If he can't fix it this time, I will go to a specialist - I never give up hope, there should be someone able and willed to do a decent job in this industry.

Stay tuned, the story continues.

And don't forget to check your gun and have your buddy check his.

Fritz
BTW: Did order a centerpin from Brownells. After all the cure to the problem is a twenty minute job for anyone who is able to lace his shoes (and owns a file)
Ordered 02-19-2010 arrived today 02-24-2010. Not bad, Brownells, not bad.

Does S&W still sells this gun? Couldn't find it on their site.

Fritz

Yes, a bad dream, indeed. Did contact S&W. Appearantly no reaction.

Neither did they answer my question or did assist me in any way to assure that their product I have in hand is not dangerous. Nor did they inquire in any way appearant to me to exclude that there is a threat by design on this product.

I know for sure my gun and another one having this problem. And suspect that some of the statements in the internet are releated to this design / mal-specification.

IMHO the mass of the centerpin in relation to the guns mass is this high, that a centerpin (and corresponding locking pin with their related springs) well in spec for a steel gun is disfunctional for one of the alloy guns.

IMHO from this results that there are many guns of this kind in customers hand which are a potential threat to the customers health.

IMHO any manufacturer and its distriubtor have the obligation to follow any hints that there is such a threat which after all they have created.

IMHO S&W has the obligation to make a recall on these guns or at least to inform their customers to check, wether in their individual case the springs are strong enough.

If they don't it is up to you, do judge if this is an honest mans behaviour.

At least it is illegal in Germany to behave the way the gunsmith did - for the Germans who read this, the term is "Produzentenhaftung", not to be mixed up with "Produkthaftung".

And I can't believe, that in the States it is legal that S&W doesn't react when confronted with a customer believing to have a gun in his hands being a threat to his health.

I am upset.

Fritz
BTW: Had a talk to the gunsmith. Apparently he did not take my quest for serious and simply did not realize the problem. Still not really customer oriented. But already better. He now promised to fix the problem.

Maybe you should call S&W during their business hours and ask to speak to someone in the revolver repair center. For that matter, maybe your gunsmith might want to call and ask to speak to one of their engineering staff. Might be more productive than speculation.

Anyway, I have a similar light scuff mark on the Scandium aluminum alloy frame of my M&P 340 just forward of the cylinder stop window. The cylinder is steel in my model, so I can barely make out a corresponding scuff in the finish of the cylinder just forward of a couple of the cylinder's stop notches. I'd imagine the softer finish of a titanium cylinder might allow for more of a scuffing.

Anyway, the hand used in the Magnum J-frames has a Bolt Block Pin incorporated in it. We were told (in an armorer class) that as the name implies, it blocks the bolt's forward movement, and is intended to prevent the cylinder from opening under recoil. It was developed for the .357 Magnum models.

When I showed the light scuffing on my SC J-frame to an armorer instructor during an armorer class, he said he wasn't familiar with the specific cause, but didn't feel it was indicative of a problem.

Now, interestingly enough, I've had another armorer instructor previously explain the results of watching a SC/Ti gun being fired while being recorded with S&W's high speed imaging equipment. He said the alloy frame, while strengthened by the inclusion of Scandium in the aluminum alloy, did exhibit a ripple effect across its surface under the heavy recoil of the Magnum rounds. He said it reminded him of watching how the surface of a still pond would suddenly ripple and move when a rock was thrown into it.

While I haven't taken the time to try and call someone in S&W's engineering dept about this matter, I wouldn't be at all surprised to learn that the stresses normally experienced when Magnum loads are fired in a Sc (or Sc/Ti) gun allow some flexing, expansion or 'rippling' effect to occur ... and that this might allow the cylinder to barely rub up against the frame right in front of the cylinder stop (where the frame is locked against the cylinder). I especially wouldn't be surprised if a titanium cylinder might also allow more scuffing to occur on its corresponding surface during any such contact with the Sc frame (meaning more than has been exhibited on the black finished stainless steel cylinder in my M&P 340).

I don't claim to have the answer to this question. I'm just wondering if this is an issue that only arises with the Sc aluminum alloy frames, and only because of their unique properties under recoil.

Just some thoughts which I've had while browsing this thread.

__________________
Ret LE Firearms inst & armorer

Another couple of Sc/Ti guns, too.

__________________
Ret LE Firearms inst & armorer

Where you are right you are right. Anyway, to me it would be easier to communicate via email and I can't see why Smith doesn't answer.

Apparently the problem - if it is a problem anyway - is widespread.

Can't see what part you are talking of nor can I imagine how such a device should work. Could you please shed some light on this part?

I don't have the gun at hand. But as far as I can remember, there is no interference between the hand and the centerpin. BTW Numrich lists the same centerpin for the PD340, SC340 and PD340 on the one side and the steel guns like the 640 on the other side.

Again, please try to shed some light on how this magic device "Bolt Blocking Pin" is intended to work (know this part from Ruger)

Well, please don't take offense, but I have problems in following this one.

Prove is (would be) easy. I just have to shoot my gun with a longer centerpin and a stronger spring. If the contact is gone, my theory is proven. Unfortunately the gun is with the gunsmith.

Fritz

BTW, I suppose I should have mentioned that my yoke, bolt and center pin are all within factory spec and operate normally.

My Sc frame still exhibits the scuff mark, though.

I'm still guessing (SWAG) it's likely to be due to the unique properties of the Sc - Sc/Ti frames when the really lightweight guns are chambered in the harder recoiling Magnum calibers.

Anybody seen it occur in a steel-framed gun?

__________________
Ret LE Firearms inst & armorer

pd360tre.jpg
pd360Due.jpg

The bolt block pin sticks out on one side of the hand about midway up the hand. It prevents the bolt from moving forward when the hand is in position at the moment of firing. Perhaps your gunsmith could show you the difference between hands with and without a bolt block pin, and could show you (using a revolver with the side plate removed) how this difference could have an influence on function.

There was a change in the Hand, with the newer hand for the Magnum J-frame guns listed as "229510000 $16.00 HAND J .357".

The last time I called to order a couple of spare parts, including some J-frame hands, I was specifically asked whether the parts were going to be used in .38 or .357 Magnum models. The gentleman reminded me that some of the parts, such as the hand, were different for the .357 J-frames.

I'm certainly not inclined to take offense at the opinion of anyone else.

Your gunsmith can probably better explain in person why the center pin must remain within a certain tolerance range in order to provide for proper function.

The center pin, however, being a fitted part for each revolver, must remain within a certain specification in order to function as intended. If being fitted at one end of the recommended spec range results in a lessening of the condition you're seeing, and the gun still otherwise functions as designed, then it sounds as though you will achieve your desire.

I wouldn't necessarily be in a rush to consider this condition a 'problem', though, not without receiving the input of the folks who have designed and manufactured the gun. the first response I received was that it didn't appear to indicate a 'problem'. I haven't since then felt it necessary to try and follow up by asking further 'up the line', so to speak. Maybe later, if only out of curiosity sometime.

There are any number of conditions which someone may be surprised to observe with their firearms, but which are often just a condition occurring as a consequence of normal functioning in any given design/model made using the materials involved in a particular model.

For example, there are still folks who believe that the 'ring' around the cylinder, caused by contact between the ball of the cylinder stop and the cylinder, can be (and should be) prevented and 'fixed'. This marking, called a 'stop track' by S&W, is indicative of how their revolver design operates and is a cosmetic consequence, as it were, not an indication that something is 'wrong'. It's to be expected in a properly built S&W revolver. The degree of its occurrence may vary a bit from any one revolver to another, being influenced by how the various parts and components fit in place and work together in any particular gun.

As far as communicating by email with the company? I have the emails of some of the folks, and sometimes it's not inconvenient to wait for responses, but direct personal conversations can more easily resolve so many more issues without the delay involved of back & forth exchanges.

I've had email exchanges about issues take several days to complete, and then I've had phone conversations with the CS reps, repair techs and even engineers clear up and resolve issues in less than 5 minutes. Of course, it depends on whether the schedules and daily activities of the persons involved allowed a phone connection.

A brief and concise response delivered via email can often be delivered and clarified, if need be, much more easily in person. Think about receiving an email response that merely stated, "Within normal spec. Not a problem." Then think about how a short 1-2 minute explanation might better clarify why it wasn't a problem, and how it might better set someone's mind at ease.

On the other hand, if the company was taking the time to provide an in-depth and detailed explanation for each and every person who called them to ask questions, it might be hard to find the time to go about their other business activities.

__________________
Ret LE Firearms inst & armorer

Fastbolt, after all, the fact that the phenomenon is this widespread might indicate that you are right. Will insist in getting an answer from S&W.

Thanks for your input!
Fritz

I really doubt these guns are intended for a steady diet of 357 mags. Call me a wuss but I don't think I want to go shoot a couple hundred per session in a scandium J frame. The cylinder "kissing" the frame may just be how it is and a non-issue aside from minor cosmetics.

Fastbolt, do you have a resource where I can have a look at the parts and inner workings of the 357-J-Frames?
If I had my gun at hand, no problem, I would simply dismantle it and have a look. Just can't wait to have it back!

Fastbolt, are you sure, that the centerpin is blocked? From looking at it, I can't believe it. Isn't simply the cylinder release knob blocked?

Fritz

Sorry, but I don't have an online working schematic of the J-frame's operation, especially regarding the interaction of the bolt, hand and center pin. There's a couple of more experienced revolver armorers who frequent this forum and who might have something useful in that regard, though. Maybe one of them will have subscribed to this thread and can offer something of that nature. The armorer manual I have doesn't discuss that in particular detail. It was something I wrote down in my notes during the class.

The hand's bolt block pin blocks the bolt (which connects to the thumbpiece nut, though), which pushes the center pin forward to open the cylinder.

If I recall correctly (no guarantee ), finding a way to prevent the bolt from jumping under recoil was originally one of the things involved in the 'performance' revision when earlier .44 Magnum revolvers started exhibiting that problem.

Let us know if you or your gunsmith can receive some clarification from S&W.

I never thought the question the armorer instructor when it was mentioned in the armorer class that the hand's bolt pin was incorporated in the J-frame models chambered in .357 magnum, and I didn't think to ask at what point it was incorporated.

Bear in mind that my thoughts on this matter are nothing more than guess work based upon my revolver armorer class training and examining my own M&P 340 .357 Magnum. I might be totally off base with my speculation.

__________________
Ret LE Firearms inst & armorer

me too

Fritz

Yes, this is to keep the cylinder closed under recoil on the N-Frames. The cylinder would actually unlatch (you could push it open if it didn't fall open, embarassing you). The X-frame has a sliding piece in the frame to lock the bolt. You can see it in a lock removal pic in FAQ's. Center pins "mushrooming" (and hanging up) from peening themselves on the locking bolt are not uncommon.

tomcatt51 and Fastbolt, did I get it right? There is such a device to lock the thumbpiece and the parts acting on the centerpin. But (at least in the case of the J-Frames) there is no device locking the centerpin. This is merely hold in place by its spring, or if it is in touch with the locking bolt by its spring.
Got it right?

tomcatt51, I couldn't locate the "lock removal pic in FAQ's". Could you give me a hint please?

Thanks,
Fritz

FAQ's
Post #9. I believe this is an X frame.
Thx to 500 Magnum Nut for the FAQ stuff.

tomcatt51, thanks. I see (better: I think I see ) that the hand has a locking pin blocking the bolt. This hinders the mass of the bolt (and annex parts) to act on the centerpin under recoil and thus relieves the problem.

But it doesn't hinder the movement of the centerpin in any way. The centerpin works only against its spring, and if the centerpin is fitted correctly against the spring of the locking bolt.

In the case of my gun the centerpin is somewhat short. It virtually doesn't touch the centerpin on opening and closing. The centerpin can overlapp on closing as much as the length of the "slope" on the locking bolt. Eyballed in the case of my gun a centerpin fitted to this end of the specs would reduce the free movement of the centerpin to nearly nothing - without impeding closing and opening. This would make a difference in the force counteracting the centerpins inertia under recoil.

If it will not only make a difference but the difference still is to be proven. Evident that stronger springs change things, too.

If after the cure the cylinder no longer "kisses" the frame, it is proven to have been worthwhile.

If the theory, that kind of good scandium vibrations make the cylinder kiss the frame oughta be right all the effort was in vain.

Stay tuned.

Fritz

Alternatively a highspeed film could shed some light on this. Isn't there by chance anybody hanging around having a highspeed camera and a scandium snubby at hand?

It seems a "correctly fitted" centerpin protrudes ~.010" beyond the ejector rod when the centerpin is pushed forward so it's flush with the center of the extractor.

I thought I remembered something along those lines. I picked up one of the first 629 Classics to incorporate the change some years ago and remembered looking at how it had been revised to prevent the cylinder from opening when shooting some of the heavier loads. (Alas, I came to discover that even the 'enhanced' 29 platform still wasn't exactly user friendly when it came to handloads that a Redhawk, Super Redhawk & Super Blackhawk would digest with aplomb. )

__________________
Ret LE Firearms inst & armorer

Giving the pictures of the mark in my very first post in this thread a second look, it seems strange, that the mark is not enlarging up to the edge. This supports the vibrato theory. What if it is both? The cylinder kisses the frame because the centerpin is "moved forward" under recoil and as there is this vibrato it rubs the surfaces.

Yes, yes, all and only speculation. Till proven the opposite.

Fritz

The N frames that unlatched really did unlatch and release the cylinder. My suspicion is you're seeing a combination of clearances being taken up and frame flex (vibration is flex) under recoil. Just enough that the cylinder can kiss the frame under recoil with magnum loads.

This is my guess, as well.

BTW, my center pin is pretty much fitted on the long end of the practical tolerance range.

__________________
Ret LE Firearms inst & armorer

Hello,

no really new news. Revolver is back with me. The highly reknown and reputaded master of the medival gunsmith charter simply said, that as the gun has the offical approval shooting passed (many, many moons ago), it is ruled out that there is a problem with the gun. There are no parts available, that would allow any tighter fitting.

Did talk to him. Hid did not do any testing. Just the bearucratic logic, that if it is approved, it is ok. He said the material of the SC340 is to weak to shoot 357 out of it. It will invariably bent to the point that the cylinder touches the frame.

Did try to contact S&W by mail twice without response. No further action taken into this direction for the moment.

When trying to find out who to call at S&W did learn from their site, that I have to conatct their German representative. Did call them. Did sent them pictures and a description of the issue. After their technical service (btw part of this unholy protected medival gunsmith charter, said to be the only ones able to do anything on a gun), they said, that they did not import this gun (acutaly, much the same persons did import it, but then under the name of another company that no longer exists). But if the seller would be unable to fix it, I can sent it in to them, then they will look after the gun. So far no statement whatsoever concerning the issue. Evident, they were not aware of the issue, far from being able to give a competent explanation.

This S&W representative for Germany also said that equaly well I could contact one of the members of the "club 30". These are members of the German gunsmith charter and are sepcialized on S&W. One of them has a PD340 at sale, that exhibits much the same marks as mine. I did call his attention to this. Only statement so far was, that he will wait for an offical statement. At least I can conclude from this, that he was not aware of the issue, far from awaiting a competent information about the issue. And the attitude "to wait for an offical statement" puts in doubt the will to stand for the responsabilities given by being administered the titel of a master of this medival gunsmith charter.

Did also do some reasoning. Taken the diameter of the cylinder to be 33,17mm in order to eat up the clearance of 0,15mm between frame and cylinder, the cylinder would have to stretch at the chamber of the fired round about 10%. Even not having the metalurgic data for the titanium used in manufacture the cylinder at hand, I strongly put into question the theory of a temporarily "blown up" chamber and the oscialtion theories depending on that. It would not blow up the chamber but blow it apart. Correct me if I am wrong.

Did measure the center pin installed. It has 75,35mm. The one furnished from Brownels has 76,35mm. There is 0,8mm clearance between center pin and locking pin. So they took 1mm of the centerpin in fitting it where 0,6 would have been sufficent. If you chamfer it, a tenth of a millimeter would have done it.

Unfortunately in Germany it is forbidden for me to fit this centerpin. This is reserved to the members of this mediaval gunsmith charter. And the members of this club I contacted either said, that they don't even consider the problem as the gun has passed the offical approval shooting or they say, that they are awaiting an offical statement. OK, there is one exception, the offical partner of S&W in Germany only said, I should sent the gun in to him for inspection.

Frankly, I don't trust this guy. Given the information, that there might be a serious problem, IMHO he is at charge to actively investigate the problem. Either get an autoritative information from stateside S&W, whos representative for Germany he is, or get his hand on any scandium snubby and do some testing. After all he sells the PD340 & the like affected by the issue and is the exclusiv partner of S&W in Germany.

No, I will first try to rule out my own theory of a centerpin being well in spec for a steel gun but being to short for a scandium gun. Will be back with you shortly.

But still, has anybody ever heard of an offical explanation of this phenomenon?

Fritz

The cylinder is not swelling but is simply moving up and down within it's "window" in the frame. The frame flexes a little, the yoke probably flexes more, the yoke/frame clearance is taken up, the yoke/cylinder clearance is taken up, the centerpin side clearance is taken up, the centerpin flexes, the centerpin moves forward under recoil. Add them all together and the cylinder ends up "kissing" the frame.