It sounds like you're in good shape then.
The Reloader's Code clearly says that we should stick with written, proven, tested reloading recipes. That is, use what's in the Book.
Since WSP Magnum primers are definitely NOT in the Reloading Book for .38Spcl, I approached this particular activity about as carefully as two porcupines making love.
First, I searched numerous handgun reloading websites and found discussions where this particular primer substitution had been previously made by experienced reloaders who obtained positive, acceptably-safe results. Next, I loaded at the low, low powder level. Last, when shooting the test rounds, I also took very conservative precautions that would nullify any Ka-boom event. [At least, with respect to the personal parts of myself and any bystanders.]
Still, being a generally cautious kinda fellow, I felt some discomfort with the process. Had to keep remembering that I was shooting these sparky .38s in a Model 19 Smith and Wesson revolver that regularly shoots .357Magnum rounds, so it's a rugged handgun, that one.
All in all........
I'm still gonna load 'em up and shoot 'em.