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Old 10-16-2011, 03:58 PM
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Default Parts Interchangeability between N-frame Generations

Generational Parts Interchangeability in the Smith & Wesson N-frame Hand Ejector 1915 -1998

Introduction

This article is starting with the advent of the .44 Hand Ejector Second Model to include the .455 Mark II Hand Ejector Second Model. The Triple Lock, or .44 Hand Ejector First Model is excluded except where noted as there are significant differences between that model and all successors. K-frames will be covered only when K-frame parts are not interchangeable.

The purpose of the article is to NOT encourage conversion or changing of firearms that are in any way collectible. However, there are a lot of older revolvers that can be put into service or rehabilitated and enjoyed rather than sliding around in the back of the sock drawer. All of this is my personal knowledge from taking the guns apart or reading or discussions with knowledgeable sources, and it a work in progress. If I am wrong in what I describe please let me know.

Two caveats. 1. The term interchangeable means that generally. Considering manufacturing tolerances and wear, it is possible that a part that should fit and work will not. It is also possible that the part may require fitting. Post-war guns, to me, require less fitting and you have a better chance of success. 2. When I use the term modern, I do not include MIM parts or assemblies or parts meant to work with MIM parts (such as springs).

Hammers

About the same time as the introduction of the Second Model, the shape of the bottom of the foot of the hammer was changed to allow for longer travel when fired double action. This style of hammer was basically continued up until the introduction of the short action Model 1950. While the hammers may be cosmetically different, functionally they are the same. The transitional hammer appears to be significantly different due to the cut made below the firing pin to accommodate the new style hammer block. Functionally it is also the same and can be retrofitted into earlier guns. It is not advisable to put a pre-war hammer into a transition gun as the hammer block would have to be removed in order for it to function, thus disabling a safety feature.

N-frame hammers from 1950 until the introduction of the frame mounted firing pins in the N-frame are interchangeable. There are some slight shape and checkering differences on the hammers, but these are purely cosmetic.

Needless to say, K-frame and N-frame hammers are not interchangeable.

Double action sears (Flys)

There are two types of double action pre-war sears. One has a curved font and one has a flat front. From my experience, this is only a cosmetic difference – not a functional one, so double action sears are interchangeable all the way up to the introduction of the 1950 short action guns. Also K-frame and N-frame double action sears are the same.

Fitting this part in the long action guns is, to me, the hardest part in getting a revolver to function smoothly in double and single action. The guys who did this at the factory were true artisans.

There are two widths of double action sears for the short action guns. I have never encountered an N-frame hammer that needs the wider one, but have seen several early short action K-frame guns (possibly pre-1950) whose hammer required the wider double action sear. It is something to watch for when buying or ordering parts.

Triggers

If the trigger assembly is serrated and is .265 inch wide, it is interchangeable among K, L, and N-frames. Be careful of the triggers made for the early K-frame Airweight (Model 12). Those are .240 inch approximately. I think the probability of running into one is low, but if buying parts it would be prudent to ask.

Also if the trigger is wider than .265 inch, it is interchangeable. However, there is a group of pre-war smooth triggers that is not. K-frame triggers made between the introduction of the K-frame Model 1905 Fourth Change in 1916 until approximately serial number 500,000 in the late 20’s will not work. They were designed for use with a hand that has a hump on it, and they lack the holes for the hand lever pin and for the hand lever spring. If you swap triggers, you need to swap the whole assembly as there are differences in the hand springs between pre-war and post-war.

Please note, these pre-war triggers, unless they are provable as unused parts, have probably been hand-fitted in a revolver at best and messed with at worst. Fitting them into another firearm could be difficult.

Rebound slides

Rebound slides between K and N-frames are interchangeable. The only problem here is ones made for the Victory models seem to have been hurriedly fitted and may not work well in an earlier gun. I have also seen post-war rebound slides successfully fitted to pre-war guns by having the pin for the hammer block removed.

Springs

Springs are generally interchangeable, and I have used modern springs in guns as early as 1921. Pre-war rebound slide springs are bigger in diameter that modern ones, but I have not had problems putting one in a pre-war gun. The Wolff extra-power cylinder stop spring is ideal as the cylinder stop spring for four and five screw guns. It has always fit perfectly for me and provided great operation.

Ejector rods

As we all know, ejector rod threads changed from right hand to left hand approximately 1960. The thing to remember here is that N-frame ejector rods are longer than K-frame. Right hand thread N-frame ejector rods, with the exception of the mushroom-headed rod (like the 1917’s) are hard to find. If you have one that is bent, do not throw it away. It may be salvageable. You may need it some day.

Hands

N-frame and K-frame hands as we know are not interchangeable. However, modern hands will work in pre-war N-frame guns as long as it is the type that does not have the hand with the ramp on it for the sideplate mounted hammer block. The ramped N-frame hand was used in 1930's guns such as the Registered Magnum and is extremely hard to find.

Barrels

Interchanging barrels is primarily a cosmetic issue. Barrel threads on the N-frame are the same for the time period we are addressing. Remember that you have three distinct "noses" on N-frames - square for the wide rib barrel (e.g. Model 29), tapered for the narrow rib barrel (e.g., Model 24), and round for the no rib barrel ( e.g. Model 21). Also if you swap a barrel, you may find yourself having to swap an ejector rod also for cosmetic or functional reasons.

I hope this helps. If I am wrong on something, please let me know. The goal here is to increase everyone’s knowledge. All usual disclaimers apply.

Oh, yes, one last thing. Frankengun, which has been show before.



1970's trigger assembly
Modern springs
Post WWII transition hammer
Post WWII transition thumblatch
Old hand
Old rebound slide
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Last edited by tennexplorer; 01-09-2013 at 01:12 AM. Reason: Improved paragraph on hands (hopefully).
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Old 10-16-2011, 05:16 PM
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As usual, about 1/2 of what I KNEW was wrong.....Like my Grand Dad Dewey always said: "95% of what I know someone told me, the other 5% I made up" Blessings-Dan
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Old 10-16-2011, 05:50 PM
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Excellent Burt, you never cease to amaze me with your knowledge.
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Old 10-16-2011, 06:27 PM
Hondo44 Hondo44 is offline
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Burt,

That's an amazing bit of knowledge that the majority of us would never have enough different guns and parts to be able to gleen on our own. Thank you for not only compiling it but also sharing it with us.

I'll have to digest it before I know if I can offer any feedback. But the concept is great especially that you explain "why" some parts lack interchangability. For example using a pre war hammer in a safety block post war gun: the explanation affords an opportunity to consider cutting a notch in the pre war hammer for the safety block to use in a post war gun.
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Old 10-16-2011, 06:31 PM
Muley Gil Muley Gil is offline
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I taught Burt everything I know about S&Ws.

Took me about a minute and a half...
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Old 10-16-2011, 08:17 PM
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Thank you, Burt, for going to the effort of compiling and organizing this. It will be a great resource.

I will print this and store it with my meager collection of smithing reference books.
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Old 10-16-2011, 11:59 PM
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After having read it, I'l stick with my first opinion; this article belongs in the 'notable thread' listing.
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Old 04-16-2012, 09:57 AM
Doug DeGraves Doug DeGraves is offline
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tennexplorer, great info, more than I can fathom at the moment. I ran across a triple lock at a local shop and it needs some TLC and perhap I will have a Frankengun project of my own. The problem is that this one is missing some parts. It needs the threaded end of the ejector rod. I have not had a chance to see if such a part is still available anywhere. It also will need a spring of some type as the ejector star falls back if you tip the gun back with the cylinger open. Someone long ago cut the barrel off to about 3 1/2 inches and stuck a rifle sight on it. I just happen to have a 3 1/2 barrel from a 27. The problem is that it has a slight buldge in it. I will look forward to further discussion on this. I need to look at the bore to see if it even needs a new barrel. It's marked 45 A.R.

Last edited by Doug DeGraves; 04-16-2012 at 10:01 AM. Reason: Bad typing!
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Old 04-16-2012, 08:52 PM
Muley Gil Muley Gil is offline
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Doug,

Welcome to the Forum.

I also like project guns. If you need any help with your triple lock, feel free to contact tennexplorer or me.
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Old 04-17-2012, 09:09 AM
Doug DeGraves Doug DeGraves is offline
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Thanks, Muley! I'm really torn about whether I should pursue this project. I have a hankering for shorter barrel N-frames that started long ago when I found a perfect 27-2 with a 3 1/2 inch BBL. I was astounded by the prices at the last gun show I went to, pleased that my stuff has gone up but discouraged that it woudl cost so much to get a 28 for my project gun. Then I ran across this triple Lock. I've been looking at forums and doing research about triple locks. I figure if I can first get it back into good working ordered i would worry about cosmetics later. I have a good relationship with this shop so I can get more photos and look at it in detail. I posted a photo on another thread, "new guy with a oldie" or something close. Is there a source for Triple Lock parts? The BBL is cut off to 3 5/8 inches. I was thinking about changing the frame to round butt profile. (I know, heresy in some circles.) And adjusable sights! Advice?
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Old 06-29-2012, 03:46 AM
Oyeboteb Oyeboteb is offline
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So...the m1917 S&W Revolvers would have the Hand which has the long 'Ear' along one side, for participating in the type of 'Hammer Block' used at that time..? And, with this in mind, are NOS in BrownPaper and Grease, or replacement or 'used' but useable m1917 Hands difficult to find?
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Old 06-29-2012, 02:47 PM
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No, the 1917 has the earlier style that does not have the "ear" and a modern hand can be fitted. The Brazilian contract guns that were made in 1937 have the style with the "ear" and are very, very hard to find. If your gun is a 1917 and not one of the Braxilian contract guns, it is likely that a modern oversize hand will correct the timing issue.
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Old 10-29-2013, 03:09 AM
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Old 02-25-2017, 11:29 AM
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Default N Frame Model 1917 hammer interchangeability

1. Will 1970's era N frame hammer fit a vintage S&W Model 1917?

2. Will a combination of 1970's era hammer and trigger fit a vintage S&W Model 1917?

Thanks,
Mike
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Old 02-28-2017, 12:06 AM
Muley Gil Muley Gil is offline
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Quote:
Originally Posted by mdraby View Post
1. Will 1970's era N frame hammer fit a vintage S&W Model 1917?

2. Will a combination of 1970's era hammer and trigger fit a vintage S&W Model 1917?

Thanks,
Mike
Arizona
It is possible to fit a '70s era trigger into a pre war S&W. However, the pre war Smiths use the old long action while the 1970s Smith use the short action that was introduced in 1950 in N frames. Hammers will not interchange.
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Old 02-28-2017, 07:13 AM
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There's a lot more to hammer differences than meets the eye. Following is the results of my research. I have the photos I reference below in JPG format only. If someone that can link them for posting here supplies their email to me in a PM, I'll be happy to forward.


All pre war hammers are not the same, there are two styles.

1st style: Triple Lock & WW I 1917 hammers/triggers and comparing to later pre war hammers:
1. The most obvious difference is of course the "chafe bushings" seen in the TL hammer (and trigger). This a feature of most pre ~1917 Smith hand ejectors. These are not necessary for a hammer to work in a TL, just only to be authentic (1st photo.)

2. All three of my TL hammers are .010" farther from the pivot pin hole to the very bottom edge of the hammer, than the 1917 hammers I compared them to. However, this does not appear to be a critical dimension. Although it's been variously reported that the TL hammer has an extended foot to provide the short action, the hammer feet match up perfectly when laid side by side. Therefore, I’m quite sure this claim is incorrect (see #3 & 2nd style pre war hammer below).

3. The difference is the "DA hammer fly" shape (pinned to the front edge of the hammer). In studying the action function, the different shape of the fly is responsible for the shorter hammer action of the TL hammers. If you choose to try a later pre war hammer in the TL, by all means use the original TL DA hammer fly. S&W 1852 – 1945, page 206.

4. TLs and WW I vintage 1917s have hammer and trigger mounting pins that are the same; 1.150" ctr. to ctr. The TL DA throw appears to be 1 1/8” while the 1917 is 1 ” due to the different DA hammer fly. The rebound slide and trigger pin ctr to ctr distance is also the same.

5. Another early pre war hammer like the 1917 may work, but not be authentic to the original Triple Lock action. Model 1917 hammers appear to be the same as TLs but the trigger is slightly different from TLs and appears to be like the trigger used with 2nd style pre war hammers below and will not even swap between later pre war N frames, (let alone K frames.)

2nd style pre war hammer:
About the same time as the introduction of the 44 Hand Ejector Second Model, the shape of the bottom of the foot of the original triple lock and 1917 hammers was changed which appears to be a newer way for longer travel when fired double action. It was basically continued up until the introduction of the post war transitional models when it was modified for the safety bar. (Photos 2 and 3).


1st style post war 'long action' transitional hammer:
This hammer prior to 1950 is different than the pre war due to the cut made below the firing pin to accommodate the new style sliding bar safety hammer block. While the pre war and transitional hammers may be cosmetically different due to the safety cut, functionally it's the same as a pre war and can be retrofitted into pre war guns with 2nd style pre war hammers. It is not advisable to put a pre-war hammer into a transition or later gun unless the hammer is notched for the sliding bar safety to function, or it would have to be removed, thus disabling a safety feature.


2nd style post war short action hammer:
Models of 1950 with the .375" wide spur and new shape.
These N frames have pins that are 1.240" apart and use hammers and triggers shaped like those in the last two photos. N-frame hammers from 1950 until the introduction of the 3rd style in the N-frame, are interchangeable. There are some slight shape and checkering differences on the hammers, but these are purely cosmetic.

3rd style hammers:
3rd style 1997-8 for frame mounted firing pins.
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Last edited by Hondo44; 02-28-2017 at 07:59 AM.
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airweight, checkering, ejector, hand ejector, lock, model 21, model 24, model 29, n-frame, registered magnum, round butt, serrated, sideplate, sig arms, victory, wwii

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