As others have noted, the .357 magnum operates at 35,000 psi, in brass that has the same web as the shorter .38 Special. You're not going to see any signs of excess pressure even in 23,000 psi "+P+" loads.

Take a look at .38-44 load data as some of them ran as high as 30,000 psi - in large frame revolvers designed for that pressure. Those loads are what led to the development of the .357 magnum, and the much higher pressure is why the .357 mag was made 1/8" longer.

Like the earlier .38-44 loads, the law enforcement only "+P+" loads in the 1970s were shot in revolvers designed for the .357 Magnum and were never intended for the average .38 Special.

What you'll eventually see if you shoot those kinds of loads in a J-frame or a non Model 19 K frame will be some serious loosening of the revolver.

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.38 Special is one of those rounds where you want to a) stick with published load data, and ideally b) use a chronograph to ensure you're getting the velocities you expect from the load. If you've got excessive velocity for the barrel length, then you've also most likely got excessive pressure and should back the load off a bit.