M&P Hammer Safety Dilemma: I was correct

[NH Old School]

On 12/11/2015 I started a thread regarding an old M&P I had just picked up that had the old style hammer block. This gun was probably made in sometime in the 1920's. My issue was that the hammer block was broken. I wasn't too concerned about that, since this will be a range gun only, but I was more interested in the idea that a properly working hammer block of that earlier type might improve the carry up, which was pretty bad on the revolver in question.

Just to review a little, the hammer blocks on the older guns work entirely differently than on current guns. Not sure when the change was made, but I have a 1959 Model 27 with the new style (works off the rebound slide), and a 1940 38-44 with the old style (spring set into the sideplate, partially blocks the hammer, deactivated by the hand, which has an inclined plane type of surface at the rear for that purpose). I repeat, they are entirely different parts and work completely differently.

Well, the replacement part arrived today, and I installed it. My theory was right. It does indeed much improve the carry up, to the point where it is now absolutely satisfactory. Slow cocking, either with the trigger or the hammer (double or single action) results in reliable lockup before the hammer falls on all chambers. Prior to installing the new hammer block there was not lockup in either mode on any chamber unless either the trigger or hammer was pulled very vigorously, more so than one would normally do in shooting, relying on momentum to carry the cylinder far enough for the cylinder stop to fall into a notch. Installing the new hammer block has made a difference of night and day in carry up.

I originally thought this might be the case because the hammer block, being itself a spring, pushes the hand to the left while the hand is pushing the hammer block to the right and into the sideplate. This makes any sideplay in the hand irrelevant, as it is actively pressed into the ratchet on the extractor.

So I learned something today. And I have a safer and better working gun to show for it.

 

[lamarw]

Good Job, You have to be more than pleased and a wonderful feeling of accomplishment.

 

[gordonrick]

Yes, the hammer block plunger is what pushes the hand. There is no hand spring in the trigger assembly. This was part of the 4th change in 1915. It changed again to the pre-1945 configuration at SN 497509 in July 1924. The I-frames had the same change in 1917 but I don't know when they changed again. I guess the 38/44's followed a different schedule as well.

The early 4th change trigger and hand are not interchangeable with later models as there is only one pin on the hand and no slot for the hand spring pin on the trigger. I've never figured out why this wasn't considered the 5th change, but I guess they had really dropped the "changes" reference by then.

 

[NH Old School]

Yes, the hammer block plunger is what pushes the hand. There is no hand spring in the trigger assembly.

You must be describing an earlier version than what I have. In my gun there is a coil spring in the trigger which tensions the hand, although it is a very different mechanism than the 1950's and later two pin slotted configuration that most of us are familiar with on modern guns.

My point is that the hammer block, which has no plunger as it is its own spring, pushes the hand sideways, keeping it in contact with the lug on the ratchet at the end of the trigger or hammer cocking stroke.

 

[NH Old School]

Here are photos explaining what I mean.

The first photo shows the lockwork, emphasizing the ramp like extension on the rear of the hand. This pushes a tab on the hammer block to the right as the hand moves upward upon cocking the hammer or pulling the trigger. The top of the hammer block is thus pushed back into the side plate and out of the way of the hammer.

The second photo shows the hammer block in the side plate. The tab that is pressed by the hand is labeled, as is the top of the hammer block that actually protrudes in front of the hammer until it is pressed back into the side plate.

The point I am making is that, while the hand is pressing the hammer block aside, the hammer block is also pressing back on the hand, holding it as far left as it can go, keeping maximum contact with the appropriate surface on the ratchet on the extractor, and thus much improving carry up. This obviates the need for oversized hands or new extractors when things start to wear with use.

The last two photos show the small spring and lever in the trigger that tension the hand forward. The first is a front view of the trigger, and the last is a top view showing the horizontal lever which transfers the spring power to the hand which is pivoted at the rear of the trigger.

 

[glowe]

. . . The I-frames had the same change in 1917 but I don't know when they changed again . . .

The application of the 1914 hammer block patent did occur in 1915 on the K frame revolvers, but did not show up until 1919 on the I frames. I ran across the Model 1903 change date while researching for a commentary on the 38 Perfected, which had an I frame. http://smith-wessonforum.com/blog.php?b=109

 

[NH Old School]

The application of the 1914 hammer block patent did occur in 1915 on the K frame revolvers, but did not show up until 1919 on the I frames. I ran across the Model 1903 change date while researching for a commentary on the 38 Perfected, which had an I frame. http://smith-wessonforum.com/blog.php?b=109

Say, maybe one of you guys that spent all that time researching patent dates and minor design changes could narrow down the year my gun was made a little more precisely than 1915-1942, which is all the standard catalog does for me. Pretty please?

 

[Skeetr57]

There were actually two different hammer blocks used on S&W revolvers between 1915 and WWII. The first type conforms to the Dec29 i914 patent drawings, and uses the hammer block actuating pin to also actuate the hand via a hump on the back of the hand. Around 1925 the design was changed (without a change in the patent date on the barrel) to the design using a ramp on the rear of the hand to push the hammer block into the side plate,and the hand was again actuated by a spring in the trigger. This design was used until late in WWII when the current style vertical sliding hammer block actuated by the rebound slide was adopted. I don't have a clear idea of the dates that a hammer block was installed in the N frame revolvers and the target K frames didn't get a hamme block until the mid 1920's.

 

[NH Old School]

There were actually two different hammer blocks used on S&W revolvers between 1915 and WWII. The first type conforms to the Dec29 i914 patent drawings, and uses the hammer block actuating pin to also actuate the hand via a hump on the back of the hand. Around 1925 the design was changed (without a change in the patent date on the barrel) to the design using a ramp on the rear of the hand to push the hammer block into the side plate,and the hand was again actuated by a spring in the trigger. This design was used until late in WWII when the current style vertical sliding hammer block actuated by the rebound slide was adopted. I don't have a clear idea of the dates that a hammer block was installed in the N frame revolvers and the target K frames didn't get a hamme block until the mid 1920's.

Thanks! So my gun was made between around 1925 (design change) and 1942 (Standard Catalog info by serial number).

 

[glowe]

Say, maybe one of you guys that spent all that time researching patent dates and minor design changes could narrow down the year my gun was made a little more precisely than 1915-1942, which is all the standard catalog does for me. Pretty please?

You got one reply with a ship date for 577,XXX on your other thread. DWalt stated 577,0xx shipped on 11/19/29. Unfortunately, another entry in the SWCA database shows a 577,0XX shipping in December, 1927, so late 1920s is about as close as we can get. I am sure you have read that the factory did not ship in serial number order, so the only way to be certain is to obtain a factory letter.

 

[Hondo44]

NH Old School,

Glad you were able to find the part and make the repair. And thx for the excellent F/U dissertation on this style safety operation; never seen it done better.

We can narrow down the production period of your gun by three of its features:

1. Order to replace 'mushroom' knob, with the ‘Barrel’ style (single milling cut under barrel), on all HE models, 1/22/27.

2. If the stocks are original and number to the gun (s/n penciled or stamped on back side of right stock); serial #s were stamped since 1857, always right side only, changed to penciled #s c. 1900 and back to stamped #s in 1929. Scratched, penciled or stamped on hard rubber grips and sometimes premium grips.

3.Gold plate over brass medallions ordered reinstated on wood stocks but with ‘convex’ tops on 2/11/1929; 3/18/29 changed to flush mounted, flat gold plated, and then finally changed April 1929 to flush mounted, flat chrome plated over brass thru WW II.All stock tops convex from then on except for the much later “Classics” models. Large chrome medallion K stocks c. 1930 and serial numbers in the 61X,XXX range only.

 

[NH Old School]

You got one reply with a ship date for 577,XXX on your other thread. DWalt stated 577,0xx shipped on 11/19/29. Unfortunately, another entry in the SWCA database shows a 577,0XX shipping in December, 1927, so late 1920s is about as close as we can get. I am sure you have read that the factory did not ship in serial number order, so the only way to be certain is to obtain a factory letter.

Thanks! I forgot about that earlier post.

 

[NH Old School]

NH Old School,

Glad you were able to find the part and make the repair. And thx for the excellent F/U dissertation on this style safety operation; never seen it done better.

We can narrow down the production period of your gun by three of its features:

1. Order to replace 'mushroom' knob, with the ‘Barrel’ style (single milling cut under barrel), on all HE models, 1/22/27.

2. If the stocks are original and number to the gun (s/n penciled or stamped on back side of right stock); serial #s were stamped since 1857, always right side only, changed to penciled #s c. 1900 and back to stamped #s in 1929. Scratched, penciled or stamped on hard rubber grips and sometimes premium grips.

3.Gold plate over brass medallions ordered reinstated on wood stocks but with ‘convex’ tops on 2/11/1929; 3/18/29 changed to flush mounted, flat gold plated, and then finally changed April 1929 to flush mounted, flat chrome plated over brass thru WW II.All stock tops convex from then on except for the much later “Classics” models. Large chrome medallion K stocks c. 1930 and serial numbers in the 61X,XXX range only.

Thank you sir! Unfortunately the stocks are not original. Somebody somewhere along the line put Magnas on it. Which I like better anyway. It has the "Mushroom" ejector rod end. So I guess the take home, putting the various bits of data together, is that it was made sometime around 1927. Close enough for me.

It also has an asterisk after the serial, which I believe means it's been back to the factory for something or other at some point.

Thanks guys!

 

[gordonrick]

Here are some pics of the two styles of hammer blocks for K-frames (M&Ps) prior to the 1945 improved hammer block. One is from ca. 1919 and the other is from a 1944-ish Victory. Note the plunger vs. the tab on the hammer block; the single hole on the old style trigger, and the ramp on the newer style hand.

 

[NH Old School]

Here are some pics of the two styles of hammer blocks for K-frames (M&Ps) prior to the 1945 improved hammer block. One is from ca. 1919 and the other is from a 1944-ish Victory. Note the plunger vs. the tab on the hammer block; the single hole on the old style trigger, and the ramp on the newer style hand.

So on the older style it looks like the wedge like shape of the back of the hand pushes the plunger in as the hand moves upward. I can only assume that there is a radiused shoulder, or possibly a cone shape on the plunger that pushes the hammer block aside as the plunger is depressed. Is that how it works?

I wonder if Bill Ruger took the idea of tensioning the hand with a spring loaded plunger from this generation of Smiths, and applied it to his single action revolvers.

 

[Skeetr57]

Actually, the pin that retracts the hammer block has a machined area on one side, partway down its length that retracts the block. The pin rests on a coil spring in the bottom of the hole in the side plate that tensions the pin and tensions the hand. Not only was the mid 20's design cheaper to manufacture and required less fitting, it also made the side plate easier to install, as the pin often catches on the side of the hand ans has to be pushed back some how.

 

[gordonrick]

What Skeetr said. The plunger is pushed in by the hand as it moves up. The angled cut on the plunger, in turn, pushes the hammer block down in to the recess as it is moved rearward thereby moving it out of the way of the hammer. The tension of the plunger/spring is what holds the hand against the lugs on the cylinder rather than the spring and lever inside the trigger on later models. As noted, there is only one pin on the hand and a single hole in the trigger. On the later models, the ramp on the hand did the same function. You can use a later trigger with the older single-pin hand, but not the other way round.

 

[NH Old School]

What Skeetr said. The plunger is pushed in by the hand as it moves up. The angled cut on the plunger, in turn, pushes the hammer block down in to the recess as it is moved rearward thereby moving it out of the way of the hammer. The tension of the plunger/spring is what holds the hand against the lugs on the cylinder rather than the spring and lever inside the trigger on later models. As noted, there is only one pin on the hand and a single hole in the trigger. On the later models, the ramp on the hand did the same function. You can use a later trigger with the older single-pin hand, but not the other way round.

Yes, of course I see it now. The wedge in the plunger that retracts the hammer block doesn't need to go around the plunger (like the conical section I had postulated), as the hammer block itself will keep the plunger in proper alignment. Thanks for the photo!

And of course another advantage to the later of the two designs is what I discovered to begin with: the side pressure on the hand helps significantly with proper and reliable carry up.

 

[Club Gun Fan]

Here is my Club Gun sn 0201 that has the 1914 Patented Hammer block

 

[Hondo44]

I wonder if Bill Ruger took the idea of tensioning the hand with a spring loaded plunger from this generation of Smiths.

I imagine he or his engineer just naturally came up with a spring and plunger for the Single Six cyl hand, having used it behind the trigger as well, when he decided to eliminate all flat springs from the Colt SAA design.