Actually mate, its in the description.ext file.
Create a description.ext file in you mission folder, then add the following:
class CfgWeapons
{
class M16{count=1;};
class MyWeapon{count=1;};
};
class CfgMagazines
{
class M16{count=1;};
class MyWeaponMag{count=1;};
};