Wasn’t that close to the Smith 547?
The 547 was a K. The I was slightly smaller than a J.
Shorter cylinder by a significant amount, as allowed by the shorter cartridge. The J cylinder is longer to accommodate the longer .38 Special cartridge.
In the mid 90’s when they introduced .357 Magnums into j frames at the same time they did a major rework by doing away with the hammer-mounted firing pin and introducing a transfer bar ignition, they made ALL j-frame cylinders, irrespective of caliber, at the longer yet again .357 Magnum length. IIRC the frames across the board were made slightly longer too.
I was sorry to see it, fractions of an inch do matter in a pocket carry gun.
