S&W Revolver Safety Features

[Durango_Dave]

You can't carry around a really old revolver with 6 live rounds or one may go off accidentally.
Manufacturers have resolved this problem in different ways. Ruger uses a transfer bar. I understand the how and why behind them.

Smith and Wesson uses both a hammer block and a rebounding hammer.

The top circle is the hammer block. The bottom circle is the rebounding hammer slide. They both prevent the firing pin from hitting the primer unless the trigger is pulled all the way back as the hammer hits the primer.

Just trying to understand, why does S&W use both methods? That rebounding hammer alone seems safe enough. It's far more sturdy than the tiny notch on the hammer of a half cock safety. Are there any guns that only have a rebounding hammer? I see S&W using both.

I have a S&W Model 29 made in 1988. It has the firing pin on the hammer. S&W no longer uses that design. Why? What's the problem with a firing pin on the hammer? Correct me if I'm wrong but I don't think there are any double action revolvers made anymore with a firing pin on the hammer.

These are simple questions. I'm just trying to understand revolver design.

 

[UncleEd]

Regarding S&Ws, hammer pivot pins have been known to break/snap
off, Without the hammer being held in place by the pin, it can be
driven forward to ignite a round despite the rebound feature from
the trigger return block.

 

[Mizar]

You need the hammer to clear that space (to rebound) in order for the hammer block to slide in. The rebound system by itself is not safe enough, despite the different engineering approaches - S&W with a trigger return block, Colt with a rebound lever and etc.

 

[243winxb]

firing pin on the hammer

Called a Hammer Nose. The S&W are cast & break. There is a custom, steel replacement.
Some have a spring, some dont. The strike can be in a larger area, more like a swipe, then a straight forward, fixed firing pin.

A soft metal rivet holds the hammer nose in place. I replaced two noses on my M28-2. Last was steel.

 

[fxvr5]

Correct me if I'm wrong but I don't think there are any double action revolvers made anymore with a firing pin on the hammer.

Current production Rossi revolvers have the firing pin on the hammer.

 

[alfsauve]

Many feel the SW hammer block for the firing pin models is unnecessary and remove it.

BTB. These do not stop the firing pin from hitting the primer. They only impede the hammer from hitting the firing pin. The pin itself is only held back by it’s spring.mpact a primer.

 

[Durango_Dave]

It seems to me that the transfer bar is simpler and better way to do this task. Why doesn't S&W use a transfer bar?

 

[Jim Watson]

History, man. They don't use a transfer bar because they never have.
S&W started out the Hand Ejectors with a rebounding hammer, period. They later added the hammer block and revised it again when that poor sailor got nailed by a dropped gun.

Iver Johnson apparently originated the transfer bar, Ruger used it to make single actions safe with six - after getting sued by people who managed to wing themselves with six in a conventional SA - and in all their double actions.

Colt is the clanger. After making revolvers with the Positive Safety Action (hammer block) from before WWI until 1969, they went to a transfer bar in the Mk III/V guns, while continuing the Python and Detective Special on the older pattern with hammer block. I am not familiar with the details of their current models.

 

[Mizar]

I am not familiar with the details of their current models.

Transfer bar is what they use now.
Colt redesigned their DA mechanisms entirely with the Mk III/V models and later on with the new Python - so they had the advantage
to start from the scratch so to speak. On the other hand, S&W continued to refine what was already a fine DA mechanism, so no dramatic change was needed or requested at all.
Transfer bar mechanisms are simple to design and make, that is correct. But they are not inherently better than the hammer block - one big disadvantage is that the bar is taking a beating every time the hammer is dropped and that leads sometimes (on rare occasions) to the breaking of the said part which makes the revolver inoperable until it's replaced. On the other hand, hammer blocks don't have that problem. So it's not always black and white, good and bad...

 

[alfsauve]

Anything added to the action may make it rougher and harder to pull.
I removed the block in my S&Ws because, a) it’s redundant. B) It’s a pain to reassemble. c) It might have added resistance to the DA pull.

I also wonder how well they work in non-vertical orientations? I’ll have to conduct experiments.

 

[Mizar]

So, basically you have no idea what the hammer block is for, neither how it works, but you removed it and compromised a safety mechanism on your revolver, right?

 

[UncleEd]

Anything added to the action may make it rougher and harder to pull.
I removed the block in my S&Ws because, a) it’s redundant. B) It’s a pain to reassemble. c) It might have added resistance to the DA pull.

Makes me fear what else you do to your revolvers.

But this practice alone has to be one of the most dangerous views
ever to appear on this forum.

 

[halfmoonclip]

Regarding S&Ws, hammer pivot pins have been known to break/snap
off, Without the hammer being held in place by the pin, it can be
driven forward to ignite a round despite the rebound feature from
the trigger return block.

This is the theory. Personally, the hammer pivot it pretty stout, as is the hammer toe that is blocked by the rebound slide.
I think a drop discharge is unlikely, or at least, long odds.
That said, the hammer block doesn't adversely affect function, and it was a really clever answer that didn't require redesigning the whole mechanism. I leave mine in, just because there's no good reason to take it out.
Now, anyone really troubled by the block can simply buy a Centennial; it has no hammer block.
And here's a question for the experts; does the shrouded hammer of a Bodyguard have a hammer block, since the hammer is protected.
Moon

 

[unspellable]

Webleys have a rebound block, no idea how strong it is.

 

[Slamfire]

this is the mechanism on the K frame model before the current lock works.

What you see on the cylinder hand is a flange that move up when the trigger is pulled. This is the hammer block on the side plate

this older hammer block is a spring, fixed on the bottom and the flange pushes the top aside into a recess on the sideplate. And it works till it stops working. As can be imagined, if oxidized grease or oil hold the spring down, the hammer block is defeated. I am sure there were other ways to defeat the hammer block, these older pistols were not considered drop safe. This is the pistol, a WW2 pistol:

I have always preferred the hammer mounted firing pin.

A hammer mounted firing pin delivers more energy to the primer as it directly hits the primer. Transfer bar, or frame mounted firing pin mechanisms deliver less energy to the primer as energy is lost in each energy transfer. That is when the hammer hits the transfer bar, some energy is lost going from the transfer bar to the free floating frame mounted firing pin, and then some energy is lost in the exchange of the firing pin to the primer. It is my observation that the frame mounted firing pin revolvers have stronger mainsprings to maintain ignition energy levels. Therefore they are more sensitive to mainspring weakening.

Also, transfer bars break, and the pistol will no go bangy until you replace the transfer bar. You can see the end of frame mounted firing pin in this picture. And the stub of the broken transfer bar.

The old Colt SAA design was renowned for going bang, even after internal parts broke.

As long as the hammer rotated and the mainspring was good, you could manually index the cylinder, hold it in place, as you thumbed back the hammer and let go! The hammer was very heavy, the firing pin was on the hammer, and the mainspring was very strong. There was a lot of energy in that mainspring and firing pin mounted hammer to ignite primers.

Ignition system energy becomes more important in cold weather, the hammer mounted firing pin was just better for function in marginal conditions.

But why did it go away? A couple of years after S&W revolvers all had frame mounted firing pins, I called S&W customer service, and fussed about the change. What I was told was the S&W had automated as many of the machining processes they could, but the frame hole for the hammer mounted firing pin could not be automated. It still required a dedicated machine and person. And that was a cost driver.

Bummer.

The one on the bottom has a better ignition system.

 

[UncleEd]

Slamfire, excellent posting.

But in regard hammer mounted firing pins vs. transfer bars breakages,
I suspect the rate just might be about the same. I have no actual
statistical proof of this other than reports of both happening
infrequently.

Personally, I've only had one hammer mounted firing pin break
(hammer nose per S&W) and no transfer bars. But I won't be
surprised if one or the other methods fail in my future shooting.

 

[Jim Watson]

A friend shot a Ruger NM .45 until the transfer bar was hammered too thin to “transfer.” He filed the hammer to hit the firing pin directly. He eventually sent it in to Ruger for overhaul when the forcing cone cracked.

 

[alfsauve]

So, basically you have no idea what the hammer block is for, neither how it works, but you removed it and compromised a safety mechanism on your revolver, right?

Not sure about the logic used to make such an assumption. I know exactly what it’s for and how it works. Perhaps I should have used the word unnecessary. Even S&W didn’t deem it important enough to replace when I sent a 686 in to be rebarreled and action polished. Checking with other forums I’m in decent company on this one.

And living on the true edge of danger I have also remove the storage lock on at least one revolver.

 

[Dave DeLaurant]

On revolver safety mechanisms in general:

C&Rsenal has been doing quite a bit of primary research on the history and development of revolver mechanisms, from the Paterson Colt through the 1890s and a little beyond (they not yet reached the transfer bar era however).

Here's a couple of pretty informative videos with revolver safety mechanism discussions:

Revolver: 101

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Clips: Modern Safety Mechanisms for the Colt 1873 Single Action Army

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www.youtube.com

 

[mcb]

Some USPSA guys remove the hammer block believing it can improved the double action trigger pull. I couldn't measure the difference with any of my N-frames with a digital trigger pull scale so I left it in. I even left the internal lock in my 627. It may be redundant but I don't mind a bit of safety redundancy. It also was not the reason I did not win the USPAS Revolver Nationals... This is probably one of those Indians vs Arrows....

 

[Jim Watson]

I have known PPC shooters to remove even the little spring that tensions the bolt.

 

[UncleEd]

If the hammer pivot pin/stud is broken, the hammer no longer
is under tension by the rebound housing; it then may go
forward and strike a primer if the hammer block is missing.

Pivot pins have broken; S&W on its latest generation revolvers
has beefed up those pins to lessen the chance of breakage.
This according to an extensive review by The RevolverGuy.

Any gain in getting a better trigger by removing the hammer
block is inconsequential.

Remember, in Murphy's Law that if something can go wrong it
will; Murphy was an optimist.

 

[Mizar]

Many feel the SW hammer block for the firing pin models is unnecessary and remove it.

BTB. These do not stop the firing pin from hitting the primer. They only impede the hammer from hitting the firing pin. The pin itself is only held back by it’s spring.mpact a primer.

It is quite obvious that you don't know what the intended purpose of the hammer block is. This is a drop safety in case the rebound slide, or the hammer leg fails and it doesn't matter where the firing pin is mounted. It is operated by the rebound slide in a positive way - which means that it will always work as intended, no matter in what position your revolver is - barrel up, down, turned sideways and etc. And to call such a safety mechanism "unnecessary" or comparing it to the hammer lock is a little bit ignorant.
It is true that hammer blocks on S&W revolvers are sometimes removed while chasing a better DA trigger (reset actually) but what you are missing is that those are competition guns, 99% of the time with extremely bobbed hammers, which makes the possibility of hitting that hammer hard enough if the gun is dropped very unlikely. But this is purely a race gun modification, that is unsuitable for carry or hunting revolvers, because it's dangerous - those same competition guys and gunsmiths know that rather well.

 

[alfsauve]

I stand aside in this debate. Mizar and other say it's dangerous. To err on the side of safety please consider it dangerous.

 

[halfmoonclip]

• Yesterday at 10:20 PM

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• #15

this is the mechanism on the K frame model before the current lock works.

What you see on the cylinder hand is a flange that move up when the trigger is pulled. This is the hammer block on the side plate

this older hammer block is a spring, fixed on the bottom and the flange pushes the top aside into a recess on the sideplate. And it works till it stops working. As can be imagined, if oxidized grease or oil hold the spring down, the hammer block is defeated. I am sure there were other ways to defeat the hammer block, these older pistols were not considered drop safe. This is the pistol, a WW2 pistol:

Slamfire, thank you for a concise explanation of how the older hammer block works; there have been previous discussions of this that left me perplexed. I can see the new system is more failsafe.
Moon