Originally Posted by Hondo44

Leatherhead23,

The convoluted I and J frame evolution of the 1950s lacked research and correct documentation in the books for many years and that caused confusion.

There are three I frame variations and two frame sizes, (because 1 & 2 are the same size, just different mainsprings):

1. Pre war and Post war Transitional with leaf spring
2. Improved I with coil spring
3. Model 1953 NEW I frame forging


And 2 J frame size variations, but both have the same cyl window size:

Baby J
Model of 1953 NEW J frame forging

All vintages of J frames have an 1/8" longer cyl window than I frames, which determines them to be J frames. Neither trigger guard size nor grip frame length determine the frame size.

So there are two I and J frame grip frame sizes:

Pre model 1953 Transitional and Improved I frames, and Baby J frames have the same size grip frame lengths and grips interchange, (and same small trigger guards).

Model of 1953 NEW I frames and NEW J frames forging, again both have the same NEW 1/8" longer grip frame length, and larger egg shaped trigger guards. Since these grip frames are the same size, grips will also interchange.

I hope this is helpful,