SC 340 Marks on Cylinder and Frame

[Fritz007]

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

 

[tomcatt51]

http://smith-wessonforum.com/s-w-smithing/94072-faqs.html
Post #9. I believe this is an X frame.
Thx to 500 Magnum Nut for the FAQ stuff.

 

[Fritz007]

Freedom for the Centerpin

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?

 

[tomcatt51]

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.

 

[Fastbolt]

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.

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. )

 

[Fritz007]

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

 

[tomcatt51]

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.

 

[Fastbolt]

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.

 

[Fritz007]

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

 

[tomcatt51]

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.

 

[Fritz007]

tomcatt51, so far I could neither verify nor rule out my hypothesis of inertia forces being the culprit.

Friend of mine, also a member of this unholy gunsmith charter, threw in the longer centerpin for me, just to omit legal issues. New centerpin measures 76,25mm as opposed to the 75,35mm of the factory fit one. Unfortunately this did not do the trick. Magtech and S&B factory loads as well as my 5.5gr of Titegroup with a 180gr Remington SJHP load produced the effect of the frame kissing the cylinder.

For the next visit to the range I made from an old feeler gauge blade a device to easily block the center pin. If - as you suppose - the effect persists, my theory is falsified. Stay tuned to get the results from the range.

Further observations are:
- My Titegroup-load did produce the weakest kiss. The colour on the frame only was smeared after 35 shot as opposed to a real clean mark after one single round of S&B or Magtech factory ammo.
- Did run the 5.5gr Titegroup through Quickload. Though it is in the limits of Hodgdon's load data Quickload says it is above SAAMI (still CIP conform, so in Germany it is in spec to shoot it).
- My "weak" titegroup load grouped not too bad (given me being the shooter) at 25m. Shot 35 rounds, all in an 10"x10" square.
- The S&B and Magtech factory loads (5 rounds each) produced keyholes. As I shot them last, I am not sure, wether all of them were on paper. At least I could identify 5 keyholes scattered over the paper.
- As I wrote in another thread, the quite heavily recoiling load with 15gr of LilGun before the Remington SJHP 180gr bullet also produced keyholes. Then I attributed this to the transsonic effect. BTW this is also a load conform to Hodgdons load data.

Evident, I will shoot any of these out of that gun only if with the locking device in place the Titegroup load ceases to produce the cylinder-frame-kisses.

IMHO, as the ones responsible for marketing this gun as well in Germany as in the States are informed about the issue, as the issue seems to affect more than only my gun, there should be an offical and authoritative action been taken by the persons marekting this gun and its only cosmetically varied succesor. Can it be that a customer has to investigate on wether the use well within specs is dangerous?

Fritz

 

[Fritz007]

Been at the range today. Before I could try to shoot the gun with the locking device in place I simply lost it

So this test still due.

Then did shoot again the Sellier & Bellot factory ammunition (158grs FMJ, conforms to CIP). Three out of five rounds keyholed. Same with the magtech (158 swc, conforms to SAAMI).

Had a kind of mild reload with me. Remington SJHP 180gr before 11.9gr of LilGun, thus more than one grain below Hodgdons min load. Did not keyhole, did group well.

Did try and block the centerpin with a flattened 22lfb case that was lying around on the floor. Cylinder did not kiss the frame when I fired my last Sellier & Bellot. Test to be repeated to verify or falsify.

BTW: In reading and rereading the S&W-Site I can't identify a phone number which I could call to get authoritative information about the gun.

Stay tuned.

Fritz

 

[Fastbolt]

S&B .38 Spl ammunition? One of the other instructors told me of a recent range qualification session where a fellow trying to use a box of that ammunition had several bullets jump their crimp and stop the cylinder from turning under recoil, and this was standard pressure ammunition.

It's not hard to call the factory in the US. The main US number is 800 331-0852. Explain to the receptionist that you're calling from Europe and ask to please be connected to one of the technicians in the revolver repair department instead of the regular customer service extension. The technicians are sometimes busy and you may have to try a couple of times to find one near the phone, unless you feel like leaving a number for them to call.

You know, if you want a small .357 Magnum revolver which has a more rigid frame (under recoil), perhaps you should consider trading your Scandium aluminum alloy framed revolver (with the titanium cylinder) in for one which has all-steel parts as far as the frame, cylinder & yoke are concerned. Just a thought.

 

[44Steve]

Sandium Frame Titanium Clyinder

Hi, Steve here. Have had the same problem . I have a 329PD , and HOT 44mag. loads caused it. Other than the line marks , no harm done , still scarry. Do call S&W ,great people to work with.

 

[Fritz007]

Hello,

Did call S&W, 1-413-781-8300 is the number for international support. The person on the phone told me, that the marks are as "serious" as the cylinder ring. The keyholes, much to the contrary, are a problem that should be verified by a competent gunsmith. Well apparently my gunsmith did not detect this or, if so, did not juge this to be a problem.

Had again a chat with S&W's German representative. They don't have sold enough of these guns to have any experience of their own with this phenomenon or it-might-be-a-problem. Especially they believe, that these guns are rarely - if not to say never - used for a continous diet of 357 on the range. Not being sure wether it is worthwhile it was said that the gun could be examined to try and diagnose a whatsoever problem. Based on common sense the advise was to try and simply identify loads that the gun can handle and not to use anything stronger.

So, where am I now?
After learning the proper grip technique I can say that it is no problem to shoot this 12oz-gun continously in 357magnum. So from my side as the shooters side the scandium snubbies is good to use potent ammunition.

My gun much to the contrary evidenced not to be able to handle the two very common factory loads of 158gr. This IMHO excludes the possibility to shoot 357magnum from this gun without further investigation.

Will still try and rule out (or verify) my "centerpin theory". Idea behind my theory is, that recoil and inertia (as opposed to pressure, pressure induced shock waves and oscillation) is the problem.

If this is ruled out, I consider the experienced problems as inherent to this species of guns and not a individual problem of my gun - individual problem which I eventually simply would ask the person who sold it to me to fix.

If it is a "feature" I will identify the heaviest load where the gun shoots properly and meters well. As for now the SJHP 180gr before 11.9gr of LilGun seems to be valid starting point for this load development.

What not is an option for me is to practice with a weak load and acutally carry a hot load. POI varies considerable between my 38special and 357load, the heavy loads shoot about 14" higher at 15yards - this was to be expected. Not to talk about follow up shots. No Sir, you should practice with the ammunition you intend to carry.

What still strikes me is, that I have to actively investigate on this and that an easy available advice "don't shoot 357magnum without sorrow investigation and individual load development out of this gun" is not available. Could it be, that the keyholing is "unknown" if it ever were to be a common "feature" of this breed of gun?

Wait, perhaps I am already gone to far. I suppose that the keyholes have the same cause as the cylinder kissing the frame, i.e. in the end the lightweight materials. Anybody has any opinion on that one?

Fritz

 

[gbw]

Herr Fritz, I've no knowledge of your problem or any possible solution.

But I have enjoyed your recountings of your efforts, both technical and political. The most valuable feature of your posts, by far, have nothing to do with your revolver. Rather it is your very well written saga of trying to deal with bureacracy and bureaucrats. We in the U.S. are on an accelerating path to the same fate, sooner rather than later. (It seems to me your gun is seriously amiss, especially given the keyhole problem. That is NOT ok. I can safely say I would never buy a used lightweight magnum revolver.)

How is it you are able to carry a gun in Germany? Thanks for your work, and best of luck.

 

[44Steve]

Titanium Cylinder

Hi, Steve here again. I just now noticed your marks on the cyl, they are different than mine . My marks are on the top strap and run the length of the cyl. and run along the chamber . I am sure the titanium cyl. expands a lot,again scarry.

 

[Fritz007]

Hello,

News, not very robust yet, but news.

Have been at the range with this blocking device (basically a piece of a 0,8mm feeler gauge blade to block the center pin).

One shot Magtech 158gr factory ammo (SAAMI compliant) without the device and had the cylinder kiss the frame. Device installed, shot one round - no kissing marks. Shot a cylinder (five rounds) no kisses.

One shot S&B 158gr factory ammo (CIP compliant) without the device and had the cylinder kiss the frame. Device installed, shot one round - no kissing marks. Shot three rounds, device flew off, but up to then no kisses. Unfortunately could not find the device on the ground in the leaves - it is an outdoor range in the woods.

Though the test has to be redone with more shots to be reliable, I dare to see my hypothesis of the different inertia forces due to different specific weights of centerpin and the rest of the gun being the culprit as at least supported by evidence.

If I can confirm these findings, then..., yes, what then?

Guess, that the specs of the springs plus the center pin (in my case there was nearly one milimeter wasted) and the shooting technique make the difference.

I can now easily shoot this gun. And feel the difference in recoil of the different loads - e.g. SAAMI vs. CIP. I can shoot it because I use the Pachmayr Deccelerator and I grip low. With the bantam grips and gripping high (the normal centenial grip) the gun would move less rearword - but sharply bite the web of your hand. And in a ransom rest, the picture is probably completely different. Might be, that this is the way the gun passed the official test. They never hold the guns in their hands, they shoot from a fixed rest. Any contributions as to this?

Stay tuned,
Fritz
P.S.:
Just let me add, that I hold the gun firmly - I can make follow up shots with much the same speed as with my Ruger GP160 - but I hold the gun low and the arms slightly bent, thus allowing a rearward and uppward movement without altering my hands grip on the gun. No need to regrip or the like.

 

[Fritz007]

Am I right, that in a ransom rest there is virtualy no axial moment of inertia acting on the center pin as there is only a rotation?
And even in a rest that would allow under recoil a movement along the barel and hence the center pins axis, the mass of the clamping device has to be added to the mass of the gun. Thus, as this device never will be made of a light scandium alloy the difference in the inertial forces between the light gun and the heavy center pin will be lost.
After all, as soon as you shoot from a rest, you will not be able to detect the problem.

Well, IMHO the gun still should be save to shoot freehanded. Am I wrong?

Fritz

 

[Fritz007]

Did try and test my hypothesis again. Replaced the grips with kind of a wooden stock, the weight of the wood is 1.4 kilogramm per liter. Thus the frames relative and absolut mass was augmented. Did not fix the problem.

Thus the theory I developed in this thread is ruled out.

The German representative of S&W did ask me to send the gun to them. Even legaly not responsible they want to investigate the problem as they say they back up their products.

Stay tuned.
Fritz