I would add a caution on just picking up all the 9 mm you can find on the range. The use of 9 mm Major in USPSA open division guns needs to be considered. These guys are pushing a standard 9 mm case to the limit to make the major power factor.

I have seen many a case which is split or bulged out at the back.... and worse.

Be selective if the range where you are "harvesting" brass has USPSA competitions there Even if the cases look fine.... who knows to what degree the case has been stressed.