Howdy
The I frame 32 Regulation Police at the bottom of this photo was made in 1925. It is chambered for 32 S&W Long, and I included a couple of rounds in the photo as an illustration.
The gun at the top of the photo is a J frame Model 63 22/32 Kit gun.
The cylinder of the 32 RP is barely long enough for the 32 S&W Long rounds. I do not have any 32 H&R Magnum rounds laying around, but Cartridges of the World tells me they are .155 longer than a 32 S&W Long. That is simply too long for the I frame cylinder.
So, why doesn't S&W make an I Frame 32 H&R Magnum?
First off, Smith has not made any I frames for years. Secondly, in order to accommodate 32 H&R in a cylinder the same diameter as an I frame, the cylinder would have to be lengthened slightly, and so would the frame.
Yes, I do know a little something about machining and manufacturing, and I can tell you that Engineering modifications such as this take time to get the design right, and time is money. And S&W simply does not seem to be interested in new designs for niche revolvers. They have not been for quite some time.
Much as I hate to say it, Ruger seems to be much more open to coming up with new designs than S&W.