S&W m327pc (problem child)

[serialsolver]

It I hijacked the thread on m327 ammo and thought maybe my problem 327 should be in a separate thread. Here's a recap with a update below. When I got the 327 it had a mark on the bottom of the frame.

I noticed after shooting some lead bullets followed by some copper bullets the rounds were not hitting the center of the forcing cone.

The center pin is floating letting the cylinder unlock and hit the frame. The frame was marked and test fired. The marker was transferred to the cylinder.

The 327 was sent back to s&w who replaced the cylinder and yoke. Once I received the 327 I test fired it and it was still unlocking.

Here's the update. I tapped the end of the ejector for a 6-32 screw.

Then cut a hi power mag disconnect spring in half and shortened the center pin so the screw and spring would fit. Here's a before assembly picture.

Here's a picture of the new center pin support.


There should not be anymore center pin floating on the 327. I'll test it out when I get a chance.

[farscott]

The picture showing the transfer of the Dykem shows another problem with the cylinder notches and the bolt. The wear on the bolt and the cylinder notch should not be there.

Your revolver unlocking reminds me of the experience of silhouette shooters and how that led to the development of the "endurance package" for the M29 and M629 .44 Magnum revolvers. I assume the lighter weight of the alloy frame and titanium cylinder are creating the same issues in the "lesser" .357 Magnum. S&W went to larger bolts and corresponding notches in the cylinder, heavier springs, and radiused/beefed up pins. With an 8-shot cylinder, I suspect the cylinder notches cannot be deep enough to stop the bolt from unlocking under recoil.

[1slow]

This takes me back to the late 1970s when S&W turned out some revolvers that would skip cylinder chambers in fast double action use.
I had hoped S&W would not screw up revolvers again.

[LSP972]

With an 8-shot cylinder, I suspect the cylinder notches cannot be deep enough to stop the bolt from unlocking under recoil.

Concur. And I think the main reason for this is the fact that the front end of the center pin is unsupported.

Moot point; it is what it is. But that brings us back to the "carry a lot, shoot a little" mantra.

.

[farscott]

Concur. And I think the main reason for this is the fact that the front end of the center pin is unsupported.

Moot point; it is what it is. But that brings us back to the "carry a lot, shoot a little" mantra.

I do not understand the comment on the center pin support. Is this in reference to the lack of support at the ejector rod end? If so, is that necessary with the crane lock, assuming (may be a bad idea) that the rear portion of the pin (ejector star) is controlled by the hand at the breech? After all, Ruger revolvers use a crane detent lock and allow the ejector rod to float without experiencing any unlocking issues.

I believe that S&W also had to beef up the hands as part of the "endurance package". That makes sense as part of an effort to support the rear end of the ejector star and center pin.

[serialsolver]

I tesf fired the 327 the other day. Same procedure, mark the revolver with a sharpie then fire som 357 mags in it. Here's the before pictures.





After shooting 22 rounds the cylinder stayed locked and the barrel stayed tight. It doesn't sound like much but for this revolver it is an accomplishment.





Also after 18 rounds of 357 mags and 6 rounds of 38+p+ the cylinder is flame cut.

[serialsolver]

This 327 has the endurance package mentioned above.

The ball lock on the yoke only keeps the cylinder closed. The lack of support for the center pin at the end of the ejector allows the center pin to float at firing unlocking the rear of the cylinder. Or another way to say it is the revolver recoils away from the center pin unlocking it like pulling the bullets from the cases. This is why the center pin needs support at the end of the ejector and the reason for tapping the end of the ejector for a set screw to hold a spring to support the center pin.

[LSP972]

I do not understand the comment on the center pin support. Is this in reference to the lack of support at the ejector rod end? .

Yes. The yoke lock is not a "bad idea"... when used as originally designed, as a SUPPLEMENT to the fore/aft locking system.

My contention is that the un-locked front end of the center pin (which the ejector rod rides over), in addition to floating axially as SS notes (i.e., unlocking on its own) is also moving a bit in the radial axis... which is causing these rub marks on the frame at the cylinder stop window. Of course, that (radial movement of the cylinder) would also mean the cylinder fit on the yoke barrel is loose, or the entire cylinder/yoke assembly has some slop; without being able to examine the thing, I'm only guessing here.

SS, have you noted any endshake/cylinder or endshake/yoke?

BTW, farscott, the "bolt" is what S&W refers to the rear locking piece in the frame that the thumb piece is attached to. What you're calling the bolt is actually the cylinder stop.

It would appear that SS's mod to stiffen the ejector rod paid some dividends... although the gas cutting on the cylinder face is a very bad thing on a titanium cylinder.

.

[LSP972]

Double tap..

[farscott]

Yes. The yoke lock is not a "bad idea"... when used as originally designed, as a SUPPLEMENT to the fore/aft locking system.

My contention is that the un-locked front end of the center pin (which the ejector rod rides over), in addition to floating axially as SS notes (i.e., unlocking on its own) is also moving a bit in the radial axis... which is causing these rub marks on the frame at the cylinder stop window. Of course, that (radial movement of the cylinder) would also mean the cylinder fit on the yoke barrel is loose, or the entire cylinder/yoke assembly has some slop; without being able to examine the thing, I'm only guessing here.

SS, have you noted any endshake/cylinder or endshake/yoke?

BTW, farscott, the "bolt" is what S&W refers to the rear locking piece in the frame that the thumb piece is attached to. What you're calling the bolt is actually the cylinder stop.

It would appear that SS's mod to stiffen the ejector rod paid some dividends... although the gas cutting on the cylinder face is a very bad thing on a titanium cylinder.

.

Thanks for the correction on the S&W terminology. For some reason (Colt-speak, perhaps), I think of the cylinder stop as the bolt.

I need to think my way through the recoil sequence to understand what is happening. I know the case head is being pushed out of the cylinder charge hole and is stopped by the breech face. That suggests the cylinder is being pushed forward (equal and opposite reaction), which explains the addition of the spring-loaded pin for the front of the ejector rod. Okay, that all makes sense.

How did S&W not catch this issue during validation/verification testing of the design before starting mass production?

My memory of flame cutting on the titanium cylinder was that it is fatal. Once the hard protective clear coat is breached, the underlying material is VERY prone to erosion. I would not be surprised if S&W would not replace the revolver due to the number and severity of the issues.