S&W M 40 Locked Up

[rainbowbob]

I took my S&W Model 40 Centennial to the range today, loaded it, and managed to fire all five rounds before it locked up on me!

That's never happened to me before and I'm at a loss to know why it happened. I had been planning to send it in to the factory to address another problem, and still plan to do so.

The trigger wouldn't move, and the cylinder wouldn't open.

I finally got the cylinder open by pressing the latch AND depressing the trigger just enough until finally the cylinder opened.

I could not find anything wrong with the cases I ejected.

Any ideas on what the problem is?

 

[SwampWolf]

Limpwristing.
Seriously, there are two things I'd try to eliminate as the culprit before sending it back to Smith. First, check the ejector rod to be certain that it's screwed in tightly. Secondly, check thoroughly underneath the ejector star to determine whether there might be a flake of powder or two that could cause the cylinder to bind. Good luck in any event.

 

[rainbowbob]

Thanks for the suggestions. The ejector rod seems to be tight, and it's clean under the star.

 

[SaxonPig]

Still locked up when unloaded?

 

[MrBorland]

Hammer mounted firing pin? Could be the pin's jamming into (or even piercing) the primer. It'd produce the symptoms you describe. Is the tip of the firing pin bent? Does the hammer/firing pin rebound as it should when the trigger is fully released?

Were you shooting factory ammo? Reloads? Any chance they were very underpowered - e.g. primer-only rounds?

 

[rainbowbob]

Still locked up when unloaded?

No. And I was unable to replicate the problem - even after reloading the same cases and dry-firing.

Hammer mounted firing pin? Could be the pin's jamming into (or even piercing) the primer. It'd produce the symptoms you describe. Is the tip of the firing pin bent? Does the hammer/firing pin rebound as it should when the trigger is fully released? Were you shooting factory ammo?

It does have a hammer mounted firing pin. But it's never done this before or since. It rebounds normaly. I was shooting factory L&B 158 gn .38 special.

 

[LordDunsany]

Two internal problems can cause lockup in an S&W revolver, both having to do with the rebound mechanism.

First is that lack of internal lube is causing the rebound block to not move fully forward. Second is related issue, that of insufficient strength in the rebound spring.

One other possibility is having lint or other junk inside the mechanism, again not allowing the rebound block to move fully forward.

I have personally repaired several Smiths with 'lockup' and this has been the cause in every case; either grit/lack of lube or a weak rebound spring.

Removal of the sideplate plus cleraning and lubing the internals should fix this if the rebound spring is not too weak. A home-done trigger job can cause this problem if coils are removed from the rebound spring.

Ron in Texas

 

[Old Fuff]

With a model 40 it can be a case where the grip safety is still blocking the hammer. Another possibility is that the cylinder stop isn't resetting, and if the cylinder can't rotate nothing else will move either.

If the cylinder latch isn't releasing the cylinder try pushing the thumbpiece backwards before trying to push it forward. Last but not least, a piece of something that shouldn't be there may be inside, blocking something that needs to move, but can't.

Previous owner gunsmithing can also play a part. Send the gun back to S&W and let them diagnose the problem. Someone's got to get inside and look.

 

[rainbowbob]

I greatly appreciate the thoughtful and knowledgeable responses describing in detail the inner workings specific to this revolver. What a wealth of information exists here.

A friend from THR has provided me with the contact info for a well thought of S&W specialist in our area.

Although I'm sure the company could do the job, they aren't offering any incentives and shipping is an added expense.

The opportunity to hand over my Smiths to an expert and talk about the specifics seems like a good idea - and a good excuse to take a ride in the country and do some shooting with my friend.