The magazine value can be halted, but when you hit the total ammo or some certain points when the server detects the halted values, it will force close the client.
These new point peer/client checks are from the beta testing (which I was apart of for both closed and open) where people were blatantly hacking and posting their hacks on YouTube for everybody to see. Super-Speed, No-Reloads, Infinite Ammo, Stat manipulation, which was all client side. The Dev's took this very seriously, and this is what they came up with as a fix. I was one who suffered in the DZ due to the excessive abusive hacking. My only recommendation to them was, people who go "rogue" should appear on the map permanently so they can be avoided or hunted respectfully. The server is always doing a value check from peer to client verifying, also, at any time your friends can join you, so the you are always alone or always with company is half truth both ways. The only really "Alone" area is the Base of Operations, which is where you and only you are allowed to be, all other areas are tagged as open world in theory. Just a little fyi.
Good luck Agents, stay safe out there.