My $.02 is even though the .38 Super will fit in a .357 Magnum/.38Special chamber, it's best not to fire it unless it's the only option you have or you have had the cylinder modified (like colt saa) to accept the cartridge. I had a 642 cylinder modified for 9mm moonclips and it shot 9mm +P (a higher pressure round) just fine, even though the barrel was marked .38 Special +P.
Also, the semi-rim on the .38 Super is so small, I could see the extractor star not having enough grip surface to reliably extract the cases.
Factory .38 Super ammo is loaded to pretty conservative pressures, especially ammo in the 1150-1250 fps range. Custom loaders, such as Georgia Arms or Buffalo Arms have much higher pressure rounds that should ONLY be used in guns chambered specifcally for .38 Super.
If you still have the case of ammo, PM me with the details and maybe we can make a deal.