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

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.

Deep into writing this article, I learned that S&W had incorporated a new drop safety into the No-Lock frame of the Mountain Gun. Smith & Wesson did away with the internal lock, but they used the space to add an additional drop safety in the same area. It explained why the “arch” of the new style frame was maintained.

There is much less going on with the new drop safety than there was with the internal lock. The drop safety parts consist of a single plate and a small coil spring (the hammer appears identical to the MIM hammer used with the internal lock). The plate has a raised post at its rear that fits into a hole in the frame to anchor it. A tab sticking off its’ front engages a slot cut into the frame wall to keep it in place. There is a “nub” on the plate that rides in the groove on the left side of the hammer, like the locking tab did on the internal lock.

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

Thanks for posting the information, and photo of the new drop-safe mechanism. I preferred the earlier frame profile too. I guess it's just easier/more economical for S&W to keep the IL profile for the time being. If no lock production is successful, wouldn't be surprised to see S&W go back to the original frame profile in future. Some years ago, I had one of the earlier 686 Mountain Guns. Not a thing wrong with it, so of course I let it get away from me. Missed it afterwards, but prices to replace it had risen to a level I didn't want to pay. I bought one of the 686 MGs. Seems a decent gun so far..

Interesting article but I can't go along with the idea that the new drop safety is due to California regs as the Lipseys are not on the approved roster as of now. Also, he seems to be implying that S&W believes the existing drop safeties aren't effective. Maybe they read my recent post about the lock flag falling out on it's own as I was cleaning my 629 MG.

Yep. S&W'S Hammer Block has been more than good enough for what, 80 years now? And CA legislators says S&W needs to keep a neutered version of the IL even though Ruger and Colt never needed it at all? Weirdness.

Its all about profit. It costs money to retool for a different size frame.

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.

S&W distributor exclusives generally aren't submitted to the CA handgun roster, most likely because they're usually batch vs continuous/regular production items.

The 642442/632/432UC are the distributor exclusive, no-lock exceptions to this.

I remember Lipsey's Jason Cloessner saying on a podcast that aluminum J-frames were notable asking S&W revolvers in that S&W can manufacture them in big volumes.

The MGs may simply not be made in sufficient quantities to justify CA roster submission. Lipsey's/S&W are selling every MG that they can ship even without California in the sales mix.

So more unnecessary parts to remove then.

That drop safety would immediately hit the trash can were I to buy a new one........Hammer block as mentioned 80 years old works fine.

Mike SC Hunter said:

That drop safety would immediately hit the trash can were I to buy a new one........Hammer block as mentioned 80 years old works fine.

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I took mine out right away, and replaced the hollowed/lightened floating firing pin with a tool steel one from Power Custom. Saved the parts in case I ever want to sell the gun.

Mike SC Hunter said:

That drop safety would immediately hit the trash can were I to buy a new one........Hammer block as mentioned 80 years old works fine.

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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.

413Maxwedge said:

Yep. S&W'S Hammer Block has been more than good enough for what, 80 years now? And CA legislators says S&W needs to keep a neutered version of the IL even though Ruger and Colt never needed it at all? Weirdness.

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No, the CA legislation just specifies the gun must pass a drop with the hammer cocked from 1 meter onto concrete. As long as the gun in question passes, it doesn't matter how the manufacturer chose to address the requirement. Be thankful that S&W revolvers still have a pretty nice SA trigger pull. Ruger and Colt SA pulls are much heavier, by design, to adapt to the drop test. The S&W SA hammer sear notch is only .004" deep, so it is easy for the hammer to get bumped off this sear if it receives a hard impact. Changing their existing SA sear design would destroy the nice SA trigger pull Smiths are known for. So Smith chose another route rather than destroy their nice SA trigger pull.

When the hammer is cocked, the hammer block is retracted and disabled...as it was designed to do. The hammer block is a drop safety designed for hammer down condition. The new drop safety shown is designed to prevent firing pin impact if dropped with the hammer cocked.

So, I guess that means that come 1-1-26 all S&W revolvers without the new drop safety will be de-listed in California.

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.

Well I guess I'll be a guineapig then I'm leaving all the factory lockwork parts in my 686MG. I've shot it with Federal and Underwood .357 ammo, and a Remington and PMC .38 Spcl. ammo; no light primer strikes or misfires. Even though there have been no light primer strikes, the DA on the MG is noticeably lighter than on a couple other 686s I have. I like it. We'll see how it goes over time...

shawn mccarver said:

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 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.

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With all due respect, you have a fundamental misunderstanding of the mechanics involved. The length of the firing pin is irrelevant, as is the fact it is floating. The mass of the S&W revolver's tiny firing pin isn't sufficient to overcome the pressure of the firing pin reset spring, so it cannot move forward to ignite a primer from inertia. If the hammer strikes the firing pin the gun will fire. The new drop safety is there to address the NEW requirement that wasn't mandated or even thought of prior: being "drop safe" while the gun is COCKED with live rounds in the cylinder. Prior to this, the concern prompting the addition of the hammer block was drop safety while the gun was uncocked but sufficient impact to the back of the hammer overcomes the rebound lug on the hammer and rebound slide.

The issue with light strikes is merely a factor of hammer velocity, and to the extent that the frame mounted firing pin can contribute to light strikes, it is due to the added friction of a moving part sliding inside a bore vs the old integral hammer nose. Today, I don't see any evidence of the frame mounted firing pin being more prone to light strikes than the old hammer nose, given mainspring tension and hammer travel being equal in comparison.

The goal of the new drop safety is to prevent the hammer from striking the firing pin in the first place... from cocked position. Again, the original hammer block prevents the hammer from doing so when the hammer is down. The new drop safety prevents it from moving forward out of cocked position if dropped on the hammer. The device doesn't need to "know" anything; it works under the laws of inertia. The device has a hinge pin on the aft end of the plate. The plate can swing upwards in an arc, where a lug on the plate pivots up into the notch on the hammer. In normal use, it stays down, out of the way of the notch by spring pressure, with the lug riding inside a radiused raceway on the side of the hammer. When dropped upside down on the hammer, inertia causes the plate's mass to overcome the spring pressure that would normally keep it held down, which then engages the notch in the hammer, arresting the hammer's forward movement.

Yes, it is true that if the hammer sear ledge forcefully disengages from the trigger, the trigger is returning to reset position, and this does move the hammer block back up into "safe" position... however, it may not do so as rapidly as the hammer swinging towards the firing pin. The hammer can beat it to the firing pin before the hammer block has a chance to stop it. In normal operation, the hammer block is moving into position just as the rebound block lug rebounds the hammer back away from the firing pin. Since it is designed to prevent the hammer from striking the firing pin when the hammer is down, it doesn't matter that it returns to position after the hammer has already struck the firing pin because it was designed to not impede firing during a deliberate trigger pull and it was not designed to arrest a moving hammer from cocked position, only uncocked... because the original thought process is that nobody is idiotic enough to be carrying the gun around with the hammer cocked over live rounds in the cylinder.

Hey, don't get me wrong; I'm not defending the value of the new device. I think it's dumb that there are so many devices to compensate for unsafe gun handling and stupidity. I'm just explaining the reason the device is there and why S&W was compelled to add it. They are a business and must sell as much product as possible to bring shareholder returns.

The 629 and other N frames appear large enough to not have the profile from rear of frame to top of grip changed. The 629 appears to have the "pre-lock curvature" while the L, K and J frame are still afflicted.

I'm no fan of CA. A truly horrible state in every way and I'm counting the days. However I thought the reason for the hammer block was to ensure it would be set in place ahead of the hammer fully dropping from SA sear notch - that it would be inter-positioned between the frame and hammer and prevent discharge? Not always fast enough, perhaps?

I certainly don't have the training to question how S&W addresses CA requirements. I suppose all I can say at this point is that I'll buy the old stuff and leave the new to others. The new Model 36 almost had me though.

dsf said:

I'm no fan of CA. A truly horrible state in every way and I'm counting the days. However I thought the reason for the hammer block was to ensure it would be set in place ahead of the hammer fully dropping from SA sear notch - that it would be inter-positioned between the frame and hammer and prevent discharge?

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No, the hammer block is a passive drop safety designed to block the hammer from being forceably moved forward toward the firing pin when dropped with the hammer down. That was/is the most likely scenario where the gun would be dropped. It doesn't reliably move into "safe" position betwen hammer and frame fast enough to always block a hammer propelled forward by the mainspring from cocked position.

Thaddeus Beauregard said:

No, the hammer block is a passive drop safety designed to block the hammer from being forceably moved forward toward the firing pin when dropped with the hammer down. That was/is the most likely scenario where the gun would be dropped. It doesn't reliably move into "safe" position between hammer and frame fast enough to always block a hammer propelled forward by the mainspring from cocked position.

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I found the previous posts here that were bouncing around in my head - true, hammer at rest only:


Getting back to the drop test question. The device just eliminated from some S&W revolvers was a "storage lock" and not a safety device. Question - did CA test storage lock equipped revolvers with the lock engaged? This seems counter intuitive, that CA would have instead tested in a condition capable of being fired. If the revolvers were tested with the storage lock not engaged, why is it now necessary to add a "safety" to replace something that wasn't used in the drop safe testing?

I suppose if CA did indeed test with the storage lock engaged, something else must be put in its place.

Thaddeus Beauregard said:

because the original thought process is that nobody is idiotic enough to be carrying the gun around with the hammer cocked over live rounds in the cylinder.

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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.