Smith & Wesson Break Top Action Conversions by Bill English

[Doc Hawken]

 


Subject :  S&W Conversion
 
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Smith & Wesson Break Top Action Conversions



One of the drawbacks to shooting the S&W Single Action Break Top revolvers (i.e. Schofields, Russians, NM #3's and their clones) rapidly is the fact that one must completely remove the trigger finger from the trigger while cocking the gun.  The reason for this is that in the 1870's S&W changed the design of their lock work on the S&W American from a Hammer Actuated Cylinder Stop to a Trigger Actuated Cylinder Stop.  No one knows why for sure but it would appear that it was a cost savings.  The change took place between the 2nd. And 3rd. Model American.  From that time on all S&W's and their clones were made with the Trigger Actuated Cylinder Stop.



What this means is originally on the S&W American the Cylinder Stop (sometimes called the Bolt) looked much like the Cylinder Stop in the Remington and Colt revolvers.  It was "L" shaped and one end was shaped to engage the notches in the cylinder in order to lock the cylinder in the firing position.  The other leg was a spring tempered protrusion that was acted upon by a cam on the hammer and would be pushed out of the way when the hammer came forward and then spring back into position for the next cocking cycle.  The trigger never comes into play on the old American, the Remington and the Colt.



The Trigger actuated Cylinder Stop is essentially a straight lever pivoted in the middle and having one end shaped to engage the cylinder notches and the other end simply resting on a shelf on the trigger.  In both cases the Cylinder Stop is spring-loaded into the cylinder notch and is positively pushed out.

In the Trigger actuated Cylinder Stop, when the hammer is being cocked, the trigger tip (sear) is required to pivot into an undercut on the hammer.  This allows the end of the Cylinder Stop resting on the trigger to pivot up and thus allows the other end to pivot down and out of engagement from the cylinder notch.  At this time the cocking of the hammer is also driving the pawl upward rotating the cylinder, which is now freed by the Cylinder Stop.

If a finger touches the trigger at this point the trigger does not pivot into the hammer undercut and thereby does not release the Cylinder Stop hence a locked up action.  The finger must release the pressure on the trigger so it can pivot into the hammer undercut and thus releasing the Cylinder Stop from the notch in the cylinder.



An additional problem here is the fact that the trigger is being pushed into the hammer undercut by spring pressure.  The trigger return spring.  This spring pressure is being somewhat offset by the pressure of the spring that is seating the Cylinder Stop in the cylinder notch.  So we have one spring fighting another spring.  A delicate balance in trying to do an action job.



The Smith Shop is now converting the S&W clones from the Trigger Actuated Cylinder Stop to a Hammer Actuated Cylinder Stop.  This essentially allows one to fire the S&W with the trigger held back just like a Colt or Remington revolver.



In picture #1 (http://members.cox.net/happytrails4461/Misc/1.JPG)  the original Trigger Actuated Cylinder Lock is shown on the left side.

The parts on the right are the hammer with the cam welded on and the new Hammer Actuated Cylinder Stop.



Picture #2 (http://members.cox.net/happytrails4461/Misc/2.JPG) is a close up of hammer cam and hammer actuated cylinder lock.  The pointer is touching the cam.  The spring leg of the Hammer Actuated Cylinder Stop is in the foreground.



Picture #3 (http://members.cox.net/happytrails4461/Misc/3.JPG) shows the 2 actions at rest (hammer down).



In picture #4 (http://members.cox.net/happytrails4461/Misc/4.JPG) we see that as you start to cock the hammer the Trigger Actuated Cylinder Lock MUST fall into the pocket in the hammer.  If you touch the trigger at all it can't and therefore the cylinder lock can't disengage from the cylinder hence "lockup".

With the Hammer Actuated Cylinder Lock like the Colt or Remington the trigger has no role in the cylinder being indexed hence it is capable of being held back while the gun is cocked.





Picture #5 – (http://members.cox.net/happytrails4461/Misc/5.JPG) -- As the hammer falls forward the hammer cam springs the leg over and it resets for the next cocking action.





Picture #6 – (http://members.cox.net/happytrails4461/Misc/6.JPG) -- The spring leg in the frame cavity.





Picture #7 – (http://members.cox.net/happytrails4461/Misc/7.JPG) -- The Hammer Actuated Cylinder Stop looking through the trigger guard opening.  None of the modification shows on the outside of the gun.





The conversion entails milling the frame under the triggerguard and in the action window.  Manufacturing and welding a hardened cam for the hammer.  Modifying the indexing hand shaft.  Manufacturing, hardening and spring tempering the new Cylinder Lock and fitting it.

Hope all enjoy reading and visualizing this unique process....Doc

[Doc Hawken]

I should get my Calvary models back from him next week...I`m very anxious to try them in the upcoming shoot. My Russians will go to Bill next.  Doc

[Virginia Gentleman]

How has this conversion been holding up during extended shooting?  Has the modification caused any unforsee problems or stress in other areas of the gun?