I can't remember what the CWP instructor told us they stood for, so I don't know. BUT - For my SD ammo, I have Hornady Critical Defense, 115 grain. I'm pretty sure this is just regular ammo (it would say +P or +P+ on the box if it was something else.. right?) Anyway - Unless you're shooting bears or elephants or something huge like that, I mean.. what difference does it make? Is mine just as good for putting someone down if needed? Or should I be trying to find +P or +P+ ? PS, my EDC is a Gen 3 G19 if that helps. Can someone explain the difference, the definitions, etc. for me? I know, I know.. I should already know this stuff.. But I forget.. and I'd rather ask on here, instead of using Google since people can share their own experiences this way. Thanks to all who reply in advance, sorry for being such an ammo noob lol OH! Also - if I should decide to upgrade to a more powerful round, what is the MAX that my Gen 3 19 can (SAFELY) handle?