Mayor - don't do that. Get a spare barrel chambered in 9mm and change the barrels when you want to shoot 9mm or the 38 Super.
This is not like firing 38 Specials in a 357 magnum. The 9mm case is tapered and the 38 Super case is straightwalled. The 9mm cases may chamber in your 38 Super barrel but most likely only because they held in place by the extractor, which can break when you do that.
We used to do the same thing years ago when 38 Super, or if we were using european mil-surps chambered in 9mm Largo or something similar, we would often find ourselves with broken extractors for the reason mentioned above.
A 9mm barrel should be cheap insurance against that type of damage for your para. In addition, the 9mms should shoot more accurately from a properly chambered pistol. HTH. Mikey.
