carrying hollow and fmj

not sure if this is the place to post this but let me know if I should post somewhere elseI'm new to the carrying thing, I'll be carrying my first gun as an armed security guard soon, some sites will be concealed, some will be open. I'm going to be carrying a glock 17since I'm new yo this whole thing, I dont really know if this is a good idea, but what's the view on having a mag of fmj along with my hollows?since I'm in a security environment, I'd have 3 mags, one in the gun, and 2 spares, is it a decent idea to carry one of those spares as fmj? in case I get in a scenario where I'm shooting at cover or armor? I doubt I'll ever need to actually use my pistol, and if I do I doubt I'd ever need my spare mags at all but just curious on the idea of this?thanks! I'm just new to the whole thing so figured I'd ask via /r/CCW https://ift.tt/2M0VikP