While 2152hq's advice is in generally valid, it is, in this case, overly cautious.

Based strictly on cylinder dimensions the J-Frame .32 cylinder has a wall thickness identical to the that of the K-frame .38 cylinder. The cylinders have been heat-treated for many years.

I have been shooting a 1967 or 1968 Model 30-1 since it was purchased in 1968. Hundreds of rounds have been fired through with loads which probably approach 25,000+ PSI, possibly higher. A very slightly higher load with the same bullet will flatten the primers so they resemble full-pressure .357 Magnum fired primers. All this with not the slightest sign of damage to the revolver!

The .32 H&R Magnum Maximum Average Pressure specified by SAAMI is only slightly higher that .38 Special +P loads that can be fired in the .38 caliber J-Frame revolver with a cylinder wall that is nearly 30% thinner!

S&W has chambered the .32 H&R Magnum in this very gun, the Model 631, which was made before the frame strengthening done to allow the J-frame to be chambered for .357 Magnum. The strength issue concerning chambering the J-Frame to .357 Magnum was with the frame, not the cylinder! While I would be somewhat hesitant to suggest chambering a Model 30 made much before 1968, and certainly never an I or Improved I Frame, There is no reason to be concerned with doing this to a J-frame gun.

There have been hundreds, if not thousands of Model 30s re-chambered to .32 H&R with no problem I have ever heard of.

Arch,

I am not recommending that you make this change, just that there will be no harm in doing so as long as you don't get ridiculously silly with your loading. If you stick to published data everything will be fine, and you will even be able to somewhat improve on Federal factory ammunition performance. The cartridge does very well with cast bullets in the 100-115 gr. range.

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Gunsmithing since 1961