.38 Super is obviosly longer than 9 MM, and HAS ALMOST NO TAPER. The magazine followers may be subtly different, and so some of the .38 Super mags may have some feeding issues if used with 9 MM.
9 MM mags usually have a filler plate inside at the rear, to keep the shorter 9 MM rounds from sliding back and forth inside the mag. If the slide stop contacts the bullets as they feed up ...
this is NOT a good thing.
Under recoil, the shorter 9 MM ammo may slide too far forward and with some bullet shapes, may pop the slide stop up into the slide in locked back position.
As Usual,
Your Mileage May Vary
[;{)
LAZ 1