Any easy way. Create a MP mission with just a basic NATO rifleman as player and a repeatedly trigger with this:
player removeMagazineGlobal "30Rnd_65x39_caseless_mag"; hint format ["%1", "30Rnd_65x39_caseless_mag" in (magazines player)]
Activate in game radio several times, you will see a "true" allways and no ammo dissapearing.