A few things to keep in mind.

First, the original 357 Magnum load featured a LEAD bullet. Note, lead has less friction in the bore than a copper jacket and that reduced friction is probably worth a 100 fps difference.

Second, when it was originally developed the only means of measuring pressure was the old Copper Crusher method. A method that really only measures the AVERAGE pressure but does NOT measure near instantaneous spikes in pressure.

Third, those 1500 fps velocities were probably the result out of a 10 or 12 inch barrel and longer barrels will increase the measured velocity. There is also the simple fact that the means for measuring velocity today are undoubtedly much more accurate that what was used in 1935.

So, what is a "reasonable" expectation for a jacketed 357 Magnum today. Someone referenced an American Eagle Semi Jacketed Soft Point and stated that the velocity was not given but it was a rather hard hitting load. I've shot that particular load back when the velocity was published and at that time is was listed as 1250 fps from a 6 inch barrel. This is achievable if you use a near maximum charge of H110 with a 158 grain Hornady XTP. It's also an accurate fairly hard hitting load but not one I would recommend using at an indoor range because of the loud booming report may alarm neighboring shooters. I also would not recommend this load during a "fire emergency" due to a drought, because out of a 6 inch barrel the muzzle flash is rather impressive. Personally I reserve these loads for use in my 357 Magnum rifles where they are much quieter, feature no visible muzzle flash in daylight, and get up to about 1700 fps from my 20 inch Winchester.

For my handgun loads I am perfectly willing to "give up" about 50 fps and use a much more user friendly load using Accurate #9. From my 6 inch Dan Wesson I've clocked these loads at an average of 1200 fps and they are quite pleasant to shoot.