I downloaded the latest edition of Western Powders' load data manual (version 5.0, available here) and compared the data against a previous edition (version 3.2.2) of their manual that I had used just a few years ago to develop some .357 Magnum loads for my 6" Ruger GP100. The following image shows the pages from both manuals for .357 Magnum loads using Accurate No. 9 powder:
(Version 5.0 is on the left, 3.2.2 the right. Click on the image to view the full-sized version.)
You can see that the loadings using the same projectiles have been significantly reduced in the current version of the manual. Of concern to me is the highlighted load; I had used the data from version 3.2.2 of the manual to develop my current .357 Magnum loads, eventually settling (after much experimentation) on 12.9 gr. of No. 9, with the OAL stretched out a bit to 1.61" instead of the recommended 1.58". This puts my load almost smack in the middle of the range indicated in the 3.2.2 manual.
However, 12.9 gr. of No. 9 now shows as being a full half grain beyond the maximum charge in the 5.0 manual.
The load I had developed from the 3.2.2 data is consistent in velocity, surprisingly mild in recoil for a magnum, and above all, extremely accurate. The sights on my GP100 are dialed in for that load, and I currently have about 400 cartridges loaded with that recipe.
If the data in the latest load manual are to be believed, my current .357 Magnum rounds are no longer safe to shoot. Should I be worried and start disassembling them?