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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S&WCA 1729