If the K frame was changed to accommodate 357 Magnum, when did that occur? I refer only to the length of the cylinder window in the frame and stretching of other components.
Howdy
I love questions like this.
I got out my calipers and several K frame Smiths.
From what I can determine, the cylinder widow was not changed at all to accommodate the 357 Magnum cartridge in a K frame revolver.
I measured 3 357 Mag K frames; a Model 19-3 I bought new in 1975, a model 13-2 probably made around 1979, and a Model 65-3 probably made around 1982. The cylinder window on all three was pretty much the same, given manufacturing tolerances. 1.815, 1.810, and 1.814, respectively.
Then I grabbed a few 38s. A Model 10-5 from 1968, a 38 M&P from 1938, another 38 M&P from 1939, and a 38 M&P Target model from 1917. Frame windows ran 1.810, 1.818, 1.818, and 1.817, respectively.
So a high of 1.818 and a low of 1.810. That would easily fit into a tolerance window for any manufacturing outfit, particularly seeing as the time spread is 100 years. I could have grabbed a few more 38s, but I thought that was a pretty representative sample.
But cylinder dimensions did change for the 357. The length of the cylinder for the Model 65-3 was 1.627. Remember that number. The length of the cylinders on the Model 19-3 and 13-2 was 1.672 and 1.674, respectively.
HOWEVER...........The Model 19 and the Model 13 have counterbored chambers to cover the rims of the cartridges, the Model 65-3 does not. The counterbores for the Model 19 and 13 are .045 and .043 deep, respectively. If you subtract the counterbore depths from the lengths of the cylinders of these two revolvers, you get 1.627 and 1.631. Very close to the 1.627 of the Model 65.
Visually, it is obvious there is less space between the front face of the cylinders and the frame with the 357 Mag K frames. I did not measure it, but it is obvious. That's how the longer cylinders were stuffed into frame windows the same size.
P.S. Forgot to mention, cylinder lengths for all the 38s were between 1.555 and 1.564. Most were around 1.564, the 1.555 was the old 38 M&P Target.
Couldn't resist. Here is my sample of guns for my cylinder and cylinder window measurements.