I’m not kidding you can get unlimited amount of ammo/magazine (only in lobby/hub, if you want do it in a mission get more friends).
Unlimited Ammo Guide
Step 1: Get a friend(s)
If you don’t have any friends then bye.
Step 2: Go to the shooting range
Press that ”W”
Step 3: Make it rain
Simply ask your friend(s) to drop their mags by double pressing ”R”
Then pick those mags by pressing ”F” you can pick unlimited amount of them.
Your friend(s) have to refill ammo after they dropped all of their mags then repeat the process.
Enjoy your unlimited ammo.