Why the Lock-Frame Curvature was Retained on New No-Lock Frames

[Thaddeus Beauregard]

I think some are confusing the new drop safety device with the internal lock. The new drop safety is not a replacement for the internal hammer lock; it is not a "neutered" version of the hammer lock. They are intended for entirely different purposes and function differently. The internal hammer lock is a storage device intended to make the gun inoperable until unlocked with a key. The new drop safety just happens to be located in the same place as the internal lock, but it isn't a substitute for it. Since S&W wasn't going to have different hammers MIM'ed for the internal lock vs "no lock" versions of the same guns, they cleverly adapted the new drop safety to make use of the existing lock lug raceway and notches that the internal lock uses. In doing so, it avoided them having to change the geometry of the hammer sear ledge to prevent forceable push-off if dropped on the hammer or add some other more complex device elsewhere in the action. In this way, it simplifies production and doesn't necessitate a whole host of different parts to inventory for the IL vs "no lock" guns.

There was already room inside the frame where the IL used to be for the drop safety, as well as a means of engaging the hammer already molded into the existing hammers being used. Again, the new inertial drop safety and the IL are not analogous. The IL is intended as a safeguard against unauthorized use of the guns and is not pertinent to the drop test requirements in CA and other states.

I agree that the idea of incorporating new safeties inside the gun in principle feels like capitulating to politics and are insulting to intelligence, but in this case, the new device is entirely hidden on the inside, doesn't require the slot be cut out of the frame beside the hammer, and doesn't interfere with function or feel of the action in any way in normal everyday use. I therefore saw no reason to remove it from my M19-10. I do lament the fact that if it weren't there, the previous, sexier frame contour could return, but there's nothing I can do about that.

 

[Thaddeus Beauregard]

Your posts have been excellent in explaining the reasoning and function of the new device. I'm curious about shear or failure of the new device. Under what conditions could it fail? I see dirt/rust/fouling/ice accumulation as a real possibilities tho TBH I doubt many who buy these guns will ever use them in the field under tough conditions enough for that to occur. Further, what might it foul up in the functioning of the revolver, if anything? I'm mostly thinking of ice as I've had deep cold and condensation tie up a pistol before. For most this all might be useless esoteric technical rambling but I am curious nonetheless.

Also to your point quoted above. I'll plead guilty to the charge of "idiotic". Twenty one years ago (posted here at the time) I was in a running fight with a smallish black bear which included running the gun dry, snapping on empty amidst a swarm of hounds, I having miscounted shots fired, the bear finally dying at my feet when my then-14 year old son dove over my shoulder to put the last round from a 7x57R into the bear's chest.

At one point in the fight after I chased the mortally wounded bear (it was from the first shot fired but what it could do in about 2 minutes of airtime left was a thing to behold) down a bank I found myself cocking an already cocked hammer. For reasons...one of which was, things were happening FAST. So just to say, it happens, or at least happened to me.

I'll just add that in service of saving some little remaining bit of pride I have left , I have a lifetime of experience in the field that others possibly still alive on this forum can attest to including a lot of bear killing. My point here is only to show that whatever the experience level, stuff can happen that while unlikely could muck up the works.

Whether such an additional safety is statistically valuable is a question I have no data to answer one way or the other. And I still wonder if it could fail due to the reasons stated above.

Again, thanks for your posts.

Excellent points and good question! I could see that if water were to work its way down beside the hammer and the gun used in sub freezing conditions, the lug on the device plate may hang up in ice formed inside the hammer channel. Apart from that, it requires an unusual, extra-ordinary inertial force applied with the gun being upside down to cause it to actuate. So, I see it as very benign and basically invisible in normal use. If crud gets around or behind the device, the worse case scenario I can see is that it fails to work as a drop safety in the very rare condition It was designed to safeguard against. In normal use, I don't see how the very small likelihood of it failing would ever cause problems with lockwork function.

 

[unspellable]

Years ago, my wife was starting trigger squeeze on a S&W model 10 in SA mode when she got knocked appetite over tea kettle. Came up with the hammer down and no discharge. Obvious that the hammer block got there before the hammer.

 

[3/4Flap]

Excellent points and good question! I could see that if water were to work its way down beside the hammer and the gun used in sub freezing conditions, the lug on the device plate may hang up in ice formed inside the hammer channel. Apart from that, it requires an unusual, extra-ordinary inertial force applied with the gun being upside down to cause it to actuate. So, I see it as very benign and basically invisible in normal use. If crud gets around or behind the device, the worse case scenario I can see is that it fails to work as a drop safety in the very rare condition It was designed to safeguard against. In normal use, I don't see how the very small likelihood of it failing would ever cause problems with lockwork function.

Roger.
Thanks very much. Interesting stuff for sure.

 

[Revelation]

With the new no-lock models, I've been curious as to why S&W didn't revert the frame contour beneath the hammer to the sharper curve from the pre-lock guns. It appears I now have my answer. While reading through this excellent review of a new 629 Mountain Gun, the author mentions and showcases a photo of a new drop-safety mechanism. This mechanism takes the space dedicated to the internal lock lockwork and interfaces in the same spots with the same hammers used in the IL models. I'm not especially certain why the existing drop safeties weren't considered enough, but there has been some theorizing that California's regs are to blame. Who knows. I do like the pre-lock frame contour better, but the new frame curvature doesn't look too bad in person.



Source with photos (scroll down to the New Drop Safety section):
https://revolverguy.com/lipseys-exclusive-sw-model-629-mountain-gun/

Thanks for the link, it's quite helpful. I'd sure like to see the side by side difference between the frame contours of the pre-lock vs the no lock models, so if anyone can help a brother out....

 

[roundels]

No, the hammer block would NOT work in the condition specified by the CA drop test. This new drop safety is designed to prevent the hammer from hitting the firing pin when the hammer is COCKED in SA mode. It engages the hammer by inertia if dropped, slipping into the notch in the hammer and preventing it from moving forward. The hammer block is designed to prevent impact to the firing pin when the hammer is NOT COCKED.

The existing hammer block only works with the hammer down, in the uncocked and rebounded position. The CA drop safety protocol specifies that the test be done with the hammer cocked. When the hammer is cocked the rebound slide is to the rear, thus retracting the hammer block out of the way. So no, the hammer block will not prevent the gun from firing in this condition.

While I do agree that the whole concept of the drop test is ridiculous because you shouldn't be cocking the hammer on a loaded cylinder before you are immediately ready to fire, S&W was only responding to a government requirement, if they intended to be able to sell the guns in all states. I also agree that the old frame curvature looked better. However, if you look at the mechanics of this drop safety, it will not inadvertently engage under normal use because it is held down out of the way with spring pressure, and it doesn't interfere with anything and isn't seen when the gun is fully assembled. So, it's not something to fret over... except for the fact it's another measure put in place because of stupid legislation. Other revolver manufacturers chose to adapt to the drop test requirement in different ways. Colt for example responded by designing the SA trigger pull to be heavier than necessary with an added "hook" on the hammer sear ledge of their new DA revolvers. Personally, I would rather have S&W's solution than have a unnecessarily heavy SA trigger pull.

I'm actually from the former US State of California and growing up I don't remember a rash of guns firing on their own when dropped. Maybe their current subjects are throwing them on the concrete to try and make it happen as some form of new social media challenge. After all, we are talking about the thinking impaired populace that elected Feinstein, Pelosi and Newsom. How much smarter can the next generation be?

 

[Nightowl]

I personally think California is more interested in preventing gun ownership than the firearm safety!

 

[3/4Flap]

I personally think California is more interested in preventing gun ownership than the firearm safety!

Of course.
But this technical discussion which impinges on CA law, has a value in and of itself.

 

[NY-1]

Thanks for the link, it's quite helpful. I'd sure like to see the side by side difference between the frame contours of the pre-lock vs the no lock models, so if anyone can help a brother out....

I'll have to find some better photos on this one of these days, but here's what I've come up with from the internet. The frame re-contour on the lock and post-lock guns has a much shallower curve under the hammer than the deeper curve that the pre-lock guns have. It's most noticeable on the J and K-frames.

Here are two Model 19's. Lock model on top, pre-lock on the bottom. Look at the curvature of the frame under the hammer. The older model looks nicer to me, though admittedly the new frame on top isn't horrible. Certainly not as horrible looking as being stuck with that ugly lock keyhole and hammer flag.

The worst offender are the external-hammer J-frames though. I'd imagine this was a combination of the internal lock and internal firing pin, but I'm not sure what influenced the design bloat the most. This isn't an issue on the centennial hammerless models or the humpback bodyguard models.

First a pre-lock model 36, then a lock model.

The mass of the S&W revolver's tiny firing pin isn't sufficient to [...]

Thanks for taking the time to write out that excellent explanation. That really sheds some light on why they opted to go this route.

 

[shawn mccarver]

So, I have been told I have a "fundamental misunderstanding" of the mechanics involved. Fair enough. That said, if the nub on the plate in the frame, if I understand the explanations correctly, prevents the cocked hammer from moving forward if the hammer/sear engagement fails. Fine. That means the nub blocks forward movement of the hammer.

Clearly, if the nub is blocking forward movement of the hammer, then when you want the weapon to fire, the nub needs to stop blocking the hammer. What makes the nub on the plate move out of the way when you want to fire the weapon?

 

[Thaddeus Beauregard]

So, I have been told I have a "fundamental misunderstanding" of the mechanics involved. Fair enough. That said, if the nub on the plate in the frame, if I understand the explanations correctly, prevents the cocked hammer from moving forward if the hammer/sear engagement fails. Fine. That means the nub blocks forward movement of the hammer.

Clearly, if the nub is blocking forward movement of the hammer, then when you want the weapon to fire, the nub needs to stop blocking the hammer. What makes the nub on the plate move out of the way when you want to fire the weapon?

Because the hammer has an arched groove molded into it to provide clearance for the nub. In normal use, the nub is always out of the way due to the groove, so it doesn't impede hammer movement. The device can only stop hammer movement when the gun is dropped upside down onto the hammer, where inertia overcomes the spring pressure holding it down. It is hinged at a pin on the narrow left side of the plate, allowing it to pivot. Normally when the gun is upright, a spring keeps it stationary and horizontal, where it doesn't do anything and stays out of the way of normal hammer function. The lug does not contact the hammer in normal use because the groove molded in the hammer has sufficient clearance for the lug.

Again, the safety can only engage the hammer and arrest hammer movement when the gun is dropped and lands UPSIDE DOWN, where inertia acts on the plate, which overcomes the spring load and pivots upwards (downwards by the viewer's perspective) to engage a slot in the hammer. As the gun is arrested by the fall, the drop safety device continues to be accelerated since it has a single pivot point and is not rigidly affixed to the frame. The right side of the plate can then rotate because it is only held stationary by the force of a spring. The plate's mass in motion exceeds the spring's force acting on it, allowing it to pivot on the hinge pin. When it pivots, the lug slips into one of the hammer notches molded into the side of the hammer. Here is a photo of the hammer showing the radiused raceway and the notches molded into the side of it. Next to that is a photo of the device showing the pivot point and the engagement lug. There's a sping behind it pulling it down against the bottom of the milled pocket it sits in. These pics are taken from my "no lock" M19-10.

 

[3/4Flap]

Because the hammer has an arched groove molded into it ...

Thanks for the excellent explanation and pictures. You've done good work here.
Other than the parts "below the waterline" looking a bit like rubber castings (I understand the benefit of MIM but I can't "unsee" what I see lol) I see no issues with this except possibly the previously stated ice/frost/condensation/muck. Which as far as I can tell, would then only reduce the wheelgun to the state of all of my Smiths which are pinned barrel jobs w/ the exception of my 29-9 referenced in the previous post on the bear fight.
The gizmo is ingenious and looks pretty well thought out. Keep some oil on that spring, and keep it clean and all would appear to be well.
I have numerous books on revolver mechanisms and development and one thing that never ends with wheelguns is change. Smith included. Endless tinkering. Each iteration has its pluses and minuses and all of them have warts. A fellow decides which suits him and uses them like the products of a favorite hardware maker.

 

[CH4]

Removing the lock is just the first step. S&W may choose to go back to the old design when it makes sense to do so from a profitability standpoint.

Yeah, that’s what I am thinking, hoping for.

 

[shawn mccarver]

Because the hammer has an arched groove molded into it to provide clearance for the nub. In normal use, the nub is always out of the way due to the groove, so it doesn't impede hammer movement. The device can only stop hammer movement when the gun is dropped upside down onto the hammer, where inertia overcomes the spring pressure holding it down. It is hinged at a pin on the narrow left side of the plate, allowing it to pivot. Normally when the gun is upright, a spring keeps it stationary and horizontal, where it doesn't do anything and stays out of the way of normal hammer function. The lug does not contact the hammer in normal use because the groove molded in the hammer has sufficient clearance for the lug.

Again, the safety can only engage the hammer and arrest hammer movement when the gun is dropped and lands UPSIDE DOWN, where inertia acts on the plate, which overcomes the spring load and pivots upwards (downwards by the viewer's perspective) to engage a slot in the hammer. As the gun is arrested by the fall, the drop safety device continues to be accelerated since it has a single pivot point and is not rigidly affixed to the frame. The right side of the plate can then rotate because it is only held stationary by the force of a spring. The plate's mass in motion exceeds the spring's force acting on it, allowing it to pivot on the hinge pin. When it pivots, the lug slips into one of the hammer notches molded into the side of the hammer. Here is a photo of the hammer showing the radiused raceway and the notches molded into the side of it. Next to that is a photo of the device showing the pivot point and the engagement lug. There's a sping behind it pulling it down against the bottom of the milled pocket it sits in. These pics are taken from my "no lock" M19-10.

Thank you for your excellent explanation.

 

[Revelation]

NY-1, I really appreciate you taking the time to answer my question. To be able to see the distinct differences from the photos you provided is very helpful to me. Thanks and Blessings!

 

[Taj]

I read everything twice. It still makes no sense.

S&W adopted a free-floating firing pin when it went to frame mounted firing pins. It seems to me that after that, there were huge numbers of reports on this Forum of failures to fire due to light strikes, and it seems that S&W was selling their guns with firing pins that had travel that was too short and the aftermarket people marketed firing pins with travel that was a few thousands of an inch longer to eliminate the failures to fire. If this additional system was thought to be needed, are we saying that S&Ws, whether using the original, or whether using a slightly longer firing pin are not drop safe?

Either way, what you have with the S&W frame mounted firing pin is similar to a Series 70 firing pin on a Colt 1911 in the sense that if dropped, the firing pin can go forward on its own inertia and strike the primer. Why this should be a problem is a mystery as Colt, Ruger, High Standard, Charter Arms, and others, have used frame mounted firing pins without being plagued with firing when dropped or with light strikes.

All that said, no one has explained to me how this new device, if it operates as theorized in this thread, knows to stay in the way when the hammer is cocked and the trigger is not pulled versus knowing to get out of the way when the trigger is pulled (it seems to not be connected to the trigger, and it certainly does not have a brain of its own, does it)?

Further, the hammer block ONLY stays out of the way allowing the hammer to strike the firing pin if the trigger is held to the rear. If the weapon is dropped when the hammer is cocked, then the problem is inertial firing (discussed above). If the weapon is dropped when the hammer is cocked and the hammer breaks off, there is nothing to strike the firing pin. And, if the weapon is dropped during the cocking process but before sear engagement, the trigger returns forward under the force of the rebound, thereby moving the firing pin block back into place. None of these scenarios seem to benefit from this new device.

As is apparent, I am not an engineer, so everyone who thinks they understand this can just go with the idea that I am a "dummy."

Many years ago, Herb Belin posted on here explaining why MIM parts were a good idea. I wish an engineer from S&W would explain this new monkey-business they have chosen to put in where the old internal lock was located.

Brother, you are right on on all aspects. I'm not sure I get it either unless it's just something to appease kalyfornya. The frame mounted firing pin spring is supposed to have enough resistance to defeat to possibility of an inertia generated discharge and the hammer block will not allow a hammer strike if the trigger isn't all the way to the rear.

 

[3/4Flap]

Brother, you are right on on all aspects. I'm not sure I get it either unless it's just something to appease kalyfornya. The frame mounted firing pin spring is supposed to have enough resistance to defeat to possibility of an inertia generated discharge and the hammer block will not allow a hammer strike if the trigger isn't all the way to the rear.

The inertia pin prevents discharge when the firearm lands muzzle down. If the hammer is down and the gun lands on the hammer, the inertia pin does not move toward the primer but rather stays away from it. The gizmo was added specifically to prevent firing in the event of a drop landing on the hammer while the hammer is cocked
And yeah, it does appear to be something to appease "kalyfornya" or lawyers, generally.

 

[Thaddeus Beauregard]

Brother, you are right on on all aspects. I'm not sure I get it either unless it's just something to appease kalyfornya. The frame mounted firing pin spring is supposed to have enough resistance to defeat to possibility of an inertia generated discharge and the hammer block will not allow a hammer strike if the trigger isn't all the way to the rear.

The tiny firing pin doesn't have enough mass to ever crush a primer anvil under inertia and set off a round by itself anyway, spring or no spring. If the gun is cocked when dropped, the trigger is in fact nearly all the way to the rear. The hammer block can only block the hammer if the trigger is all the way in reset position. The rebound block must first move the trigger back away from the frame so the hammer block has room to move up in front of the hammer. The specific scenario the new gizmo is designed to protect against is the hammer being pushed off the sear when cocked and is about to strike the firing pin. The hammer block, floating in the side plate channel and moved into position during the hammer rebound, was never designed to be quickly forced in the way of the hammer travel. It is moved by a tiny pin on the rebound slide, loosely moving inside an elongated slot on the tail of the hammer block. For it to be able to move that quickly to block the hammer in motion, it would need to be connected to the lockwork by very robust linkages, not merely floating in the side plate channel and pushed by a tiny, relatively fragile pin. It is and always was designed to just sit there at rest to block the hammer while the hammer is at rest. It is not an "active" safety, it is a passive safety.

 

[RebCop]

I also would like to know why the new curvature? It disrupts the classic looks of the weapon. Is there a valid technical reason for it?

 

[Thaddeus Beauregard]

I also would like to know why the new curvature? It disrupts the classic looks of the weapon. Is there a valid technical reason for it?

Yes, it began because they needed real estate beside the hammer to incorporate the internal lock mechanism, which takes up space that wouldn't be available otherwise. The old deeply curved sweep didn't provide for enough space above the cylinder release bolt for the lock. The reason the new contour still carried over to the current "no lock" guns is the subject of this thread. The new drop safety device is now in the space once occupied by the lock. Even if the new drop safety wasn't there, it doesn't make economic sense to have 2 different frame profiles, one for the IL guns and another for the "no lock" guns.

It does look like the N-frame guns were large enough that they didn't require frame modification for the locks, or if they did, it was very minimal, as they appear to retain the classic lines.