In VC 1.3 Multiplayer there is a protection against the unlimited ammo feature.
What it does:
Kills the player when he uses up around wpnmagcapacity*2 without a reload (or perhaps in a certain time, reload more likely to protect against lag).
It's a very easy protection which practically is based on an IF-"Formula".
It is possible to extend the weapon capacities, extremely much on Machineguns like the Browning or the M60, Degetarev.
However the protection doesn't include unlimited mags (because that would be "too much" to do for the devs).
The theory or in other words how VC handles Magazines is that it just shows the amount just for look (in game u see the amount).
The amount of magazines is calculated by the game by taking
totalroundsinallmags div(similar to /) magcapacity +1
always returns integer.
Conclusion:
What we need to do to make a trainer on magazines is therefore not searching for the magazine value, there is none. You got to search for the amount of rounds there is.