The very early K-frame cylinder stop was used from serial 1 - 62449 for the .38 caliber series, and 1 - 18125 of the 32-20 caliber series. At the end of these serial number series, the design was changed to a much simpler one, that resulted in the addition of the 5th frame screw in the front of the trigger guard. Instead of an engineering change, Neal & Jinks recognizes this point as the start of the Model of 1905; in fact the 1905 was introduced at serial 58000 for the .38 series, and another number for the 32-20 series, as 4-screw revolvers.

The engineering change that is the topic of this discussion happened earlier, but at this time it is not known when the change occurred.

The early version of the cylinder stop features two spring-loaded pins. One is used to return the cylinder stop to its initial position, and the other interacts with the trigger. This other one allows a finger on the front of the trigger to capture this pin, and pull the cylinder stop down. As the trigger retreats, the finger hits a bevel on the side of this pin, forcing the pin down and into the cylinder stop, so that the finger can pass over the top of the pin.

The pin ( or plunger) that returns the cylinder stop to its initial position is the subject of this posting. The following picture shows six of these early cylinder stops.



The plunger emerges from the side of the lower right corner of the cylinder stop. It is retained in the cylinder stop by a cross-pin, which rides in a milled-out portion of the plunger. This milled out area is visible on some of the cylinder stops in the above picture, making the plunger appear to have a hook on the end of it.

The engineering change involves relocating the cross-pin from above the plunger, to below the plunger, and increasing the diameter of both the cross pin and the plunger. The diameter of the plunger itself increases from about 0.075" to about 0.090" . Also, the angle of the plunger within the cylinder changes. It's not known at this time why this change was made. What is known is that the factory intentionally wanted the cylinder stop to rub against the side of the cylinder, to insure that it produced a positive lockup by dropping into the stop slot on the cylinder. Perhaps increasing the diameter of the plunger, and maybe using a larger spring, helped to insure that the lockup would be more positive.

Regards, Mike Priwer